Rat Poison

Rats are prime suspects in the vectors of several diseases communicable to humans, and gravitate to areas of dense human populations in search of food and water sources.

Rats survive by scavenging, meaning that they subsist by searching out and eating dead plant or animal materials that are readily available in their environment. When humans are less than conscientious in discarding of food waste, populations of rats will be drawn into closer contact. An abundance of discarded food will create increasing reproduction rates in the rodents, compounding the problem.

Rat infestations are generally dealt with via the use of rat poisons and traps. Rat poisons or rodenticides are a group of chemicals known to be fatal to rodents. In general most of the toxic rat poison ingredients do not cause immediate death to the animal; depending on the class of rodenticide utilized, the term of effectiveness can be from a few days to a couple of weeks.

Rats are anatomically and neurologically incapable of emesis (vomiting). Vomiting is a coordinated muscular response to toxic substances which forcefully expels stomach contents back up into the esophagus and out of the mouth. The rat esophagus is long and there is a strong barrier between stomach and esophagus which makes forceful expulsion impossible. The rat neural network lacks the connections that coordinate the diverse muscle systems (abdomen, throat, shoulders) involved in emesis. Rats are capable of regurgitation which is a passive means of material moving out of the stomach and into the throat, whereas vomiting is characterized as an active process due to unified action of muscle groups.

Because rats lack the ability to forcefully expel a contaminated or poisonous substance once ingested, they have adapted other means to avoid such materials. The rat’s first line of defense is to “sample” food in small amounts, if a small portion doesn’t make them sick, they will return and eat more of it. They also have keen senses of taste and smell—and can detect harmful substances with these markers in minute amounts. They are also capable of observing the cause and effect of one of their number dying quickly after eating a particular material, resulting in the colony learning to avoid that food in future.

Types of Rodenticides

Warfarin, also known as Coumadin and by several other brand names, is recognized by most people as a human medicine instrumental in controlling the formation of blood clots in people who are prone to them. In fact, Warfarin was first developed in the 1940s as a rat poison, only later was its beneficial medical use discovered.The best rat poison has historically been that which is odorless, tasteless and which does not have a nauseating or immediately lethal effect. This has resulted in the development of several classes of rodenticides, the most popular and enduring of which are the anticoagulant based rat poisons.

Anticoagulant rat poisons suppress the animal’s ability to metabolize Vitamin K, which is vital in the formation of blood clots. Blood clotting (when not pathologic) is beneficial; limiting the amount of blood lost from an injury and paving the way for the healing process to begin. Suppression of vitamin K synthesis results in “thin” blood unable to clot which in turn causes diffuse internal hemorrhage. In rats this process can take between seven to fourteen days to end in the desired lethal outcome.

One of the shortcomings of this class of rat poisons is that the extended death trajectory allows the animals to return to various haunts to die, many of them inaccessible to humans. Most rats killed by this method returned to their nests—which are usually in walls or roof rafters, subfloors or foundations. The unexpected consequence is structures contaminated with the odors of decomposition; sometimes for months after the poison is administered.

The first wave of anti-coagulant rodenticides were low dose; meaning they contained the rat poison in small amounts which required several feedings over many days for the animal’s body to reach lethal levels. So called “second generation” anti-coagulants were later introduced which were promised to be one dose effective and shorten the time leading to death. These rat poisons contained high doses of the anti-coagulant agent. This had the drawback of making them even more prone to secondary poisoning occurrences than the first generation poisons.

What is “Secondary Poisoning”?

Secondary poisoning refers to the exposure of non-target animals and people to the effects of the anti-coagulant ingredients of the rat poison. Wildlife and pets can consume rat carcasses—or the poison bait itself– which retain high levels of the poisons and in turn be sickened and die. Human children, especially toddlers, may encounter the rodenticide and being at that stage of human development where everything must go into the mouth to be tasted, accidentally ingest the poisons.

Secondary poisoning led to the further development of other classes of rat poison, including the use of metal phosphides; Vitamin D2 and D3 based rodenticides (which result in calcium overload affecting internal organs), Bromethalin (chemical compound which causes brain swelling) as well as sulfamide derivatives, which induce lethal seizures. None of these, with the possible exception of the phosphides, which convert to phosphine gas when in contact with rat stomach acids, are free from the stigma of secondary poisoning. Even phosphides when used as a fumigant rat poison, can be lethal if pets or wildlife are exposed to the gas.

Aside from direct exposure or ingestion, it is also possible for rat poisons to permeate soil or contaminate water sources, and thereby create another avenue for pets, wildlife and children to be exposed to their toxic effects.

How quickly does rat poison work?

The length of time a rodenticide takes to kill the rat depends on the type and class of rat poison used.

As already noted, anti-coagulant based poisons take anywhere from a few days to two weeks to work, largely dependent on which generation of anti-coagulant poison is used.

Vitamin D derivative rodenticides work by increasing calcium levels in the blood of the rat. This hypercalcemia leads to heart and kidney failure as organs and blood vessels mineralize. One feeding by the rat is usually all that is required, with death occurring between two to four days after ingestion.

Zinc Phosphide rat poison kills by means of phosphine gas being released when the substance comes into contact with the stomach acids of the rat. It can take anywhere from one to two days for the effect to occur.

Bromethalin developed in 1985 as a solution against anti-coagulant resistant rat colonies is highly toxic, designed to kill in one feeding. A neurotoxin, it attacks the central nervous system resulting in convulsions, paralysis and death. This rodenticide usually leads to a lethal outcome within 24 to 36 hours after ingestion.

To avoid the chances of accidental secondary poisoning, all rodenticides should be used only in conjunction with tamper resistant bait traps that enclose the rat poison away from the reach of pets and young children. Traps are best placed along the rat’s usual path of travel between nest and food sources.

Recognizing rodenticide side effects

The side effects of rat poison are variable, depending on which class of rodenticide is involved and whether the affected is human or animal.

Anti-coagulant side effects in humans are usually related to the inability of blood to clot after coming into contact with the rat poison. Rat poison in humans will usually require a few days for symptoms to manifest. Depending on the level of exposure (and the age and body size of the victim) this side effect may be relatively minor or may result in massive internal hemorrhage. Signs include increased bruising, nosebleeds, blood in urine or feces, bloody gums, dizziness, and fatigue. Digestive disruptions including blood tinged diarrhea and vomiting are common.

Like humans, the side effects of anti-coagulant rat poison in dogs and cats take time to manifest; they also depend on the length of exposure to the poison. A single large dose may be less toxic than several repeated ingestions due to the relatively quick excretion of the one dose in the animal’s feces as opposed to repeated, prolonged exposure.

The age and general health of the animal are factors as well. In cats onset of signs and symptoms are usually delayed to their characteristically lower exertion levels compared to dogs. Some of the most common symptoms are depression, lethargy, non-specific fevers, weakness, pale gums, confusion, cold extremities and high heart rates. Sadly, some pets will exhibit no symptoms at all, and be found dead after a sudden collapse, usually because a severe internal hemorrhage into a large body cavity, the brain or the heart occurs.

Secondary anti-coagulant poisoning has been found to be treatable in both pets and humans with doses of Vitamin K1. The length of time that the antidote must be taken can amount to several weeks for both animals and humans.

Other classes of rat poisons will present with other symptoms.

Bromethalin rat poison exposure will present with excitability, running fits, depression, seizures, and severe muscle tremors, especially in dogs and usually within 8 to 10 hours of ingestion. Also included in aftereffects: loss of ability to bark, loss of appetite, and lethargy. No antidote currently exists, but symptoms are treated with corticosteroids.

The vitamin D based rat poisons ergocalciferol and cholecalciferol work by increasing calcium absorption, eventually leading to calcium crystals building up in blood vessels and organs. Depression, lethargy and anorexia are three of the earliest symptoms to present; kidney failure due to mineralization generally occurs well into the poisoning process. Difficulty in breathing and symptoms of heart failure may also be observed.

Phosphide rat poisons (most often zinc phosphide) cause similar side effects in humans and animals. Tightness in the chest (in humans), difficulty breathing and cough; fluid in the lungs and irregular heartbeat may all be in evidence. Phosphides also cause liver failure which is detectable by yellowing of the skin and the whites of the eyes. In later stages, coma resulting from toxin build up in the brain (caused by liver failure) can occur. Fortunately phosphides tend not to build up in rat tissue, reducing the chance of secondary poisoning somewhat.

Where can I buy rat poison?

Rodenticides are widely available for purchase. Chain home improvement stores like Lowes or Home Depot generally carry a wide range of rat poisons as well as traps and bait stations. Big Box retailers such as Wal-Mart are also sources for rodenticides. Hardware stores, Feed and Grain stores as well as Farmer Co-ops also often have rat poisons for sale. Online sources abound as well.

The Environmental Protection Agency of the United States, in an effort to cut down on the secondary poisoning of wildlife, pets and children placed restrictions on certain classes of rodenticides, their sale and distribution.

In May 2008 restrictions were announced which were to be phased in to become fully effective in 2011.

These are the restrictions that affect the purchase of rat poison by consumers for personal/home use:

• 2nd generation anti-coagulant rodenticides will no longer be available for consumer purchase. Only lower dose first generation anti-coagulant rat poisons will now be available for home use.

• Only farmers, livestock owners and certified pest control technicians will be able to purchase rat poison in bulk. No bag or container of rat poison in excess of 8 pounds will be sold to the consumer market

• Loose pellets will no longer be available for home use. Nor will pastes, powders, blocks or other poisons which are not contained in tamper resistant packaging.

• Rat poisons are to be kept above ground and only in EPA approved tamper resistant bait stations.

These restrictions were resisted by rodenticide maker Reckitt Benckiser, Inc. which sells poison rat baits under the brand name “d-Con”. Reckitt Benckiser previously launched a legal appeal with three other rodenticide manufacturers, refusing to implement the new regulations.

As of January 2013 Reckitt Benckiser has found itself facing an “EPA order of cancellation” as the result of their failure to comply to the new EPA standards. This order will prohibit the sale of twelve of the company’s d-Con products. Until the cancellation is fully implemented, the affected d-Con products will remain available for purchase.

This still leaves at least 30 compliant rat poisons available to the consumer market, and provides better protections—even if they are not perfect—for wildlife, pets and children against secondary poisoning by rodenticides.

54 thoughts on “Rat Poison”

  1. I’m planning to buy rat poison from Amazon. What are the brands that you recommend Jeff? Thanks in advance!

  2. My pit bull ate some rat poised rat pallets in the basement, he begun feeling weak like he was falling asleep, about an hr after eating it. I kept giving him vitamin k at the highest dose a dog of such weight can take, and hydrogen peroxide mixed with his water. He was on vitamin k for two weeks after that. Now he’s 9. When it happened he mustve been like 3 years old.

    1. What is the point of telling us that?
      Usually you give peroxide to induce vomiting, not to mix with water.
      Anticoagulant baits cause internal bleeding which the Vitamin K helps with. Pet usually have to be on Vitamin K for 30 days.

    2. Our cat ate some rat poison in our backyard, she was very sick. Come to find out they have rat baits all over our complex, vitamin k is the answer. Thank god she is going to be ok, putting signage would of been smart.

  3. I have one very educated mouse remaining in my kitchen. He is the last of the lot that I have already gotten rid of. However, he is now aware of all the combinations of poisons, traps, and glue boards that I have used to kill the others. Therefore I am looking to buy a rat/mouse poison that is colorless and odorless. I am in NY.

    Thanks for the help.

    1. i recently discovered I had a rat in my backyard. My neighbor told me to get a rat zapper off of Amazon. After putting it in the yard, I had no luck. I then went on line to get an understanding of rats. Appearently they are pretty smart. So in order to zap them, you can’t just place a rat zapper down and expect them to go in it. They suggested I put cat or dog food out and around the zapper but turn it off for a couple of days. I did this. Then they suggested I put the food inside the zapper and don’t turn it on- I did this. Then after a week or so they suggested putting the food in the zapper and turn it on. He’s dead:)

    2. yes I’ve been using Warfarin for about 2 weeks I still have rats. I’ve seen some of there droppings are brown, and inside they are filled with blue Warfarin. Now what can I do?

  4. I have rats in my pigeon loft. They don’t eat the poison and avoid the traps. What can I do? Does rat poison expire or go stale?

  5. hi ,plzz help me i ve ratss in my house .. i tried evrythngg .. sum of them r die bt we ve still sum .. bt its only in my kitchen under ther bottom counter.. i block all the ways ..bt now i dont understand if thy die inside wt i m gonaa do … pllZzzz help me …

  6. Last year we had Terminix come out and “rat proof” all points of entry to the tune of $1000. They did a good job but the guarantee is only good for a year, needless to say our year is up, almost to the day and the rats have found (made) another point of entry, this time into my garage. They (rats) have chewed the underside (bottom) of our outside garage door (man door-wood not the large rollup-metal) and formed a “Tom and Jerry” hole. We have tried the electronic sonic devices – which are unless! I think that machine called out a message to all rats in my neighborhood to come on over.
    We have 2 dogs and a cat who have access to the garage, so poison is out of the question.
    Please help, any advise is appreciated.
    I’m in Ventura, CA and being near the beach, rats may be just a part of the beach experience!

  7. If you have a rat problem INSIDE the house, do NOT use poison. The rodent will die and you may never find the body. The decomposition of the body will reek for months.

    I have had great success with electronic traps. Bait with whatever the rodent is seeking out in your house or try dry cat or dog food, cheetos, a very small piece of chocolate with peanut butter on it, dry cereal, all are almost irresistible to rodents. The flashing light on the tap will tell you that you have caught something. It is a clean kill with no blood vs snap traps sometimes. Give it a try. They are expensive at ~$35-50 but work great indoors. They are NOT weather sturdy and must be well protected if used outside. Water will destroy the electronic traps.

  8. Fall is in the air and as the nights get cooler, Ms. Rat always finds a way in. I live in an older Craftsman home that I have sealed up to the best of my ability but they always find a way. And neighbors have ornamental plums and other fruit trees and gardens that attract them. I have finally resorted to poisons and lots of traps. I cut a small hole in the downstairs ceiling I can access to set traps and place poison between floors and put the same in the garage and outside in pet proof poison stations. I have come to accept it is part of living in an old part of town with historic homes and lush yards……rats live where people congregate. I had a rat die in the wall last year and it took about 3 months for the odor to completely go away. I found the smell more tolerable than listening to it chew wires and scamper around my house all night!

  9. Hi i have some feeder rats for my snake and one got out like a week ago. I believe he got into some rat poisoning but when i caught him and put him back in their cage my other two died and shortly after he did to. I have a lot bigger rat then the others and he seems fine. I can not feed him to my snake as it will kill the snake if he did some how get some in him but i was wondering if it was possible that the rat that got out somehow made the other two die before he did because of the poison

  10. After two years we have finally gotten rats out of basement but continue to battle them in garage and shed. I have re poured concrete in garage to eliminate entry points which has worked so far . I have regularly baited with block bait in bait stations as well as using wooden snap traps. The traps are averaging about kill a week @ the block bait is consistently taken at all times of the year. At this point I am wondering if these super rats aren’t THRIVING on the bait……. We used to see occasional dead rats when we first started baiting but now we don’t see any. They even ate a 5 lb bag of block bait that was suspended from the ceiling with bailing wire!

  11. I’m having a problem wit rats coming up in my yard from the woods behind my house I’m scared to use a rat poison because I have a pet dog what can I do in this matter they are really big rats I think they are wood rats but I’m no expert and I’m not sure

  12. I am having all my water lines replaced with pex and have heard there are instances of rats loving to chew through this material. Some even say most rat poisons cause major dehydration, and in some instances, actually encourage rats to gnaw into water lines to quench their thirst. Others say that’s a bunch of hype and pex is still the best option. Financially my options are limited (to pex)–my water lines are from the 1960’s and are corroding and breaking. My plumber says just make sure food supplies are limited and put a lot of rat poison in the attic. Here I read rat poison is a bad idea as rats die where they are poisoned and I may never find them in 10 inches of attic insulation. How in the world do you know who to listen to?? I am in south Texas and feel like I am ‘damned if I do and damned if I don’t’. Any advice would be greatly welcomed. Thank you.

    1. We live in Deer Park, Texas. For the last 4 months it has become unbelievable how bad the rats are. NOTHING IS KILLING THEM. THEY HAVE TO BE THE SIZE OF MY CHIHUAHUAS. THEY EAT SO SO SO MUCH. I’M VERY CLEAN, CLEANED MY PANTRY OUT AND NOTICED HOLES IN FOOD BOXES. FLOUR, CHIPS, DOG FOOD, ETC. ALL OF COURSE HAS BEEN THROWN OUT. EVERYTHING IS NOW STORED IN THE ICEBOX OR MICROWAVE. I’M SO PARANOID. THE DAY IS C0MING THAT THE DAMN RATS AND I are going to run into each othet!!!! Please help if you’ve had any luck!!!
      Email address is
      Newt.rudy@sbcglobal.net
      Thank you

      1. rats, mice, etc enter thru holes. find the holes & cracks, and buy aluminum tape & place over holes. they can’t chew that tape

  13. loation:Bangalore Nandinilayout there are two mouse in my kitchen. I have . Please help where I can get poison to kill these mouseplaced mouse trap since two days butnot able to catch these

  14. I have tried everything to get rid of our unwanted house guest and it seems like he is smarter than even the exterminator we hired because he’s still here and terrorizing my home I don’t even want to kill him I just want him gone please help me I live in Monroe L.A.71203

  15. For mice in the attic, my dad took a tall jar or coffee can, filled it half to 2/3 full of water and sprinkled some whole oats in it. Mice would climb in but because the sides were straight/ smooth they couldn’t climb out and would drown. Therefore no worry of a mouse dying in the walls somewhere. Scoop dead mouse out and it reset. May need to change oats if been awhile and they sprout or rot.

  16. I rent a room in a house where many small rooms have been made for rent. The place is infested with rats & last night one was trapped in my room. We have been catching many with traps & one guy has pet safe bait boxes. My dog even caught one last week. I am very worried for my own & my dogs safety. What can I do for this major infestation? In a panic, Thank You.

  17. Jeff live in an isolated area but next to a deep litter chicken house and have a serious rat problem. Today one went into my car and eat its way through my back seat. Managed to catch him. What is the most effective and quickest poison.

  18. Rat is eating the block of poison …….but seems to still be living ……not sure if it’s the same mouse or if there is more than one….to really know if it or they are dying from the poison…

  19. The government banned DDT that was extremely effective at killing mosquitoes. Other governments followed suit, and over a million people needlessly died of malaria.

    The EPA banned diazinon, which did a great job of killing ants. The substitutes are awful and require several times the amount of pesticide to do the same job, and requires frequent re-application.

    The EPA banned the rat poisons that worked, and how long is it going to be before we see an epidemic of some disease carried by rats?

  20. Question about safety: Do the poisons break down into harmless substances after the rats eat them and die, or will decomposing rat bodies in the garden or lawn continue to release poison into the ground, or perhaps harm predators which might eat the dead or dying rats? Which poisons pose the smallest risk of “post-rat” toxicity?

  21. Jeff please get back to me… Im sleeping maybe 1 hr a night… Everytime the heat comes on i think i hear stuff… Please help… I had 1 company come out 2 days ago.. Laid those black boxes with poison… Im ready to move… I cant take it!

  22. My neighbor tried to help us with our rat problem. He placed pellets along the house. We picked them up and discarded them. It appeared that rats might have gotten to some of the pellets and broke them apart. But I worry if any of the chemicals could have washed off and drained into my garden. I was furious and uprooted my entire garden. This happened in the late summer of last year. It is now spring, will it be safe to restart my garden.

  23. I am using decon bait stations and there not working. The mice are depriving me of my sleep. its 3:51 a.m. here in rossville ga, and these mice are up playing in my dresser drawers please help me!!!! I just want to enjoy a good nights sleep. Jeff if you have answers please,HELP!!!!

  24. We have a horrible rat problem in our home. The siding is rotten at the bottom so they have many entry points. We’ve killed 3 with traps in the pantry but we don’t know how many there are. They have gotten good at avoiding the traps. We need help. We live in Houston, TX

    1. You need a 3 prong attack against rat infestation and a measurable degree of determination.

      You should use:
      1. Manual kill traps – old fashioned rat traps.
      2. Sticky traps – like glue
      3. Rat poison.

      If someone is at home all the time, every time a manual trap springs into action check the trap and remove the critter, rebait and reset. Keep the traps active and vary your baits.

      Check the sticky traps in the evening, when you use the bathroom late at night and very early in the morning.

      Rat poison – don’t let the poison rut out. Check outside for rat holes and keep them baited and I’d check this several times per day. In about 10 days you should see big results. On the last infestation I had a 12 rat kill in 3 days.

      Persistence is definitely required. One can easily see where the rats travel through your home because of the droppings. This is an indicator of the “rat interstate highway” and you should place your attacks along this avenue of approach.

  25. I agree with the comments made by Joe, the government gets rid of what works in favor of crap that costs you more to get less results. My rat problem seems to be an old one house was empty for a while now that we have moved in their back finding damage as I’m renovating.

  26. Lives in a motel and they are coming in from rthe sink.and the door doesnt have a weather strip on it so they coming from the outside too.I have been here for five months dont know what else to do the poision they eat it and the traps they walk around them

  27. Hello,

    Thank you for a very interesting and educational referance file to refer to whenthere is a need to look back of what you provided to keep ” Rodent’s in check”. I have recently been invaded by these ANNOYING CREATURES and want them to RID OF ASAP.
    I am using Every Method that I can apply, Block, Pellot, Granular. I apply a base of Peanut butter on a base to then apply a coating of the loose material to be their last meal.
    I am going to create a more lEATHAL METHOD BY EXPERIMENTING TO see it work with JUst Peanut Butter.

  28. we’re having a fairly bad rat problem in our garage and attic. We’ve lived here for over 30 years and have hardly ever had rats except for a few in the attic which we systematically eliminated with snap traps. We’ve tried the snap traps again, but they aren’t working this time. and they are avoiding the d-con pellets and black boxes with the large blue blocks. Also the sticky traps were completely useless–only caught the dog several times. Can you suggest anything else? We live in Capistrano Beach, CA, a couple of blocks from the ocean. I don’t know what kind of rats these are, but they might be fruit rats, although they seem to eat anything–even my garden fertilizer which they chew through the bags to get to. Thanks for your suggestions or comment.

    1. I live in Silicon Valley and can no longer get those packets with the green pebbles etc.

      Recently I tried the black sticky traps . I put one under an antique dresser that they were hanging out at and for 2 weeks I would peek behind it every day hopping to see a stuck rat….no luck ;(

      About 2-3 weeks later I glanced behind that dresser and WHOA!! The sticky trap was gone! I found it eventually about 8 feet away from the dresser and behind a chair! Go figure that….and do not waste your MONEY!!

  29. I live in Silicon Valley and can no longer get those packets with the green pebbles etc.

    Recently I tried the black sticky traps . I put one under an antique dresser that they were hanging out at and for 2 weeks I would peek behind it every day hopping to see a stuck rat….no luck ;(

    About 2-3 weeks later I glanced behind that dresser and WHOA!! The sticky trap was gone! I found it eventually about 8 feet away from the dresser and behind a chair! Go figure that….and do not waste your MONEY!!

  30. We have a rat infestation problem in our neighborhood. They breed in one trashy back yard and then spread over the neighborhood. I have used con for years and now see that it is no longer available in CA. I also see that it is priced out of the market. Is there an outdoor rat poison that I can buy or make that is equal to the d con tray? Children and pets are no problem.

  31. We have a smart one he gets thru other boxes of cereal to the one he wants avoiding traps and glue traps. what can I do????

  32. Hi my name is James, I need to purchase Bromethalin, and ready to use bait with Bromethalin for the control of rodents that have developed bait shyness over Zinc phosphide bait.
    From Nigeria. Here is my contact +2349023924344.
    Thanks and Best Regards.
    James Dumo.

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