Just One Bite Rat Poison Review

5 minutes to read | Updated for 2018

Last update on 2018-06-18 / Affiliate links / Images from Amazon Product Advertising API

Bottom Line

Old Cobblers Farnam Just One Bite rat poison is a very effective and reliable product, which has been on the market for a long time and has seen multiple improvements to the formula. It kills most types of rats and mouse in just one feeding with a lethal dose of bromadiolone. Keep away from pets and children and don’t handle the product with your bare hands.


  • Kills normway rats, roof rats, mice
  • Best results in agricultural areas
  • Kills within a week
  • Insects can’t destroy it


  • Risk for pets and children
  • Some rats could be immune

Even those of us who have had hamsters or similar rodents as pets when we were children can understand the enormous problem that is a rat infestation.

A rat is a much more serious creature than a hamster, which can grow up to three inches or a mouse that can grow up to four, as an adult specimen can be up to ten inches in body length, with additional eight inches to their tail. Urban rats are also much beefier than rural rats, as they feed on the fast-food leftovers.

Of course, there are many ways of getting rid of rats and house mice such as bait stations, rat traps and, of course, rat and mouse poison. If you have one rat, or maybe a couple, you might consider a rat trap that deals with your issue. But, if you have a full nest with dozens of specimens, or even a couple of nests if you live in a building, there is no other way to go but poison. While throwing large amounts of poison all over your basement can seem, at times, like nuking the rats from orbit, it’s the only way to be sure.

How Does Just One Bite Rat Poison Work?

If bromadiolone was to be ever used in a human vs. human war, someone would be court-martialed.

It is technically a 4-hydroxycoumarin derivative with a chemical name of C30H23BrO4 and it is extremely poisonous to all things that have a bloodstream as it is a vitamin K antagonist and an anticoagulant that induces rapid liver failure. Thankfully, for now, rats are much smaller than humans so that there is a dose that is non-lethal to us and very lethal to them.

This, by no means, suggests that Just One Bite could be eaten and it shouldn’t even be touched with bare hands, but you will not be harmed with it just sitting there in the open. Usually, during the night, the rodents will come near the poison to smell it out, and once they get fooled into thinking that it is just a wheat cake, they will start eating it. After a few days, you will see dead rats all around as they start leaving their nest to die.

With the lethal dose of poison already in their bloodstream, with their high metabolism, it is just a question of time and even the biggest rat would be dead inside a week. As we know how Just One Bite works, placement should be an obvious choice. You shouldn’t place the poison anywhere where people live, eat, or sleep as it would both attract the rats and spread the poison itself.

The best course of action is to place the package somewhere outside, in a secluded area where the rats would feel free to eat it no matter the size of the rat. A shrub or the edge of the shed or barn would be the perfect place. Depending on the size of the place from which you wish to eradicate the rats and the size of the infestation itself you might want to place several feeding stations in several positions, as to provide all rats in the vicinity with a deadly snack.

Key Features

Active Ingredients

Just One Bite is a very potent rat poison produced by Old Cobblers Farnam that is meant to explain the efficacy of the poison in the title. The point of this rat poison—that is focused more on rats and mice that live in and around agricultural productions—is that it is both enticing for rats to eat and that it is very deadly.

The active ingredient of Just One Bite is bromadiolone, and even though it is only 0.005% of the ingredients, just a couple of bites will be more than enough to kill even the biggest rat in some time. The rest of the product is basically a cereal cake, which would be very tasty if it weren’t laced with a highly potent anticoagulant.


There are three types of risks when using any type of rat poison and that includes Old Cobblers Farnam Just One Bite. Those risks are poisoning the pets and children, spreading poison in the household, and the poison just not working. For the first risk, it is important to keep the poison out of reach of pets and children. As it looks like food on purpose, it is easy for a child or a dog to mistake it for a snack.

In this case, you should rush whoever—or whatever—ate the poison to the hospital as soon as possible and tell the medical staff there that this is a bromadiolone poisoning. While in these doses the poison shouldn’t be lethal to humans, it could create liver damage and even worse for those who already have problems with blood coagulation.

As for the poison being spread in the house, this should be prevented by positioning the rat poison outside any paths that people or vehicles traverse often. Also, you should keep your footwear clean when you know that you were passing near poison. The last part is usually confusing for most people, as we know that we are working with a potent poison.

Some rats, especially in urban environments, might have become immune to bromadiolone. Therefore, if you don’t kill the infestation inside a week, you should opt for a poison with a different active ingredient. Because of their high metabolism and some other biological traits, rats can mutate quite quickly even inside one generation, becoming immune to all sorts of diseases and poisons.

Those rats who have been in contact with less potent bromadiolone-based poisons might have survived and made their offspring immune to this particular concoction. In this case, there is nothing wrong with the product or the way you positioned it, it is just that the rats are immune and you have basically just fed them wheat cakes. If this happens, just use a product with a different poison and see how that goes.

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