The exact amount of chocolate it takes to kill a dog depends on the type of chocolate and a dog’s weight.
As a vet, I would never feed chocolate to my own dogs. Even just a little is not good for your dog.
In this post, I’m going to explain why chocolate is toxic for dogs and how to calculate exactly how much chocolate can kill a specific dog.
Why is chocolate toxic for dogs?
Chocolate contains theobromine and caffeine.
These two methylxanthine molecules, while metabolizable by humans, are not well tolerated by dogs.
Chocolate is higher in theobromine than caffeine however both molecules play a role in chocolate poisoning in dogs.
Methylxanthines have 3 main effects that you’ll notice:
- Gastrointestinal irritation: Your dog’s stomach, after ingesting a toxin, will try to expel it via vomiting and diarrhea.
- Diuretic: This means they take water out of the body and into the urine, making your dog urinate and drink more.
- Stimulant: This is why we chug Starbucks every morning- but also what causes signs like hyperactivity, increased respiratory and heart rate, irregular heart rhythm, and tremors!
Chocolate will not affect your dog instantly and signs usually appear between 2 to 12 hours after eating chocolate.
These symptoms, when mild, usually fully subside after about a day. These times may vary depending on the digestive and metabolic rate of your dog.
In most cases, chocolate poisoning will not kill your dog. However, dogs with pre-existing heart and nervous conditions have a greater risk of dying. 
You might be asking yourself, “why does chocolate harm my dog but not me?” and rightly so.
We humans, metabolize and process methylxanthines much faster than dogs and we would need to eat a huge amount of chocolate in one go for methylxanthines to have a toxic effect on us.
While the half-life of methylxanthines in the human body is about 2 to 3 hours, it takes dogs a whopping 18 hours to achieve half-life, allowing a lot of time to circulate and wreak havoc on their body systems. 
How much chocolate can kill a dog?
The table below shows the LD50 (the dose that leads to death in half of the individuals exposed to it) for theobromine and caffeine in dogs.
|Methylxanthine||LD50 as mg per kilogram body weight 2,3,4|
|Theobromine||100 – 500 mg/kg|
|Caffeine||100 – 140 mg/kg|
What the table above means is that lethal or toxic doses depend on the molecule causing toxicity, and these doses, in turn, depend on the dog’s body weight and metabolism.
By this reasoning, the same amount of chocolate would affect a Chihuahua differently to a Great Dane.
This also means that anything between 125g (4.41oz) to 625g (22.05oz) of baker’s chocolate is enough to kill a 20kg (44.09 lb) dog. 
Different clinical signs can be seen at different dosages. (see table below)
|Dosage of methylxanthines in mg/Kg bodyweight||Symptoms observed|
|20||Vomiting, diarrhea, excessive drinking|
|More than or equal to 60||Seizures|
One should also take into consideration that the methylxanthine content depends on the type of chocolate.
This means that while a quarter of a 250g (8.82 oz) packet of cocoa powder and half a 250g bar of baking chocolate can make a 10kg (22.05 lb) dog sick, a dog needs to eat more than 250g of milk chocolate to have the same effect. 
When your dog finds their way into your pantry and eats chocolate, we know that you won’t have the mental faculty to do all these different calculations.
This is why there are handy chocolate toxicity calculators like this one to make your life much simpler in such emergencies.
What about white chocolate?
As seen in the chart above white chocolate products contain a very small amount of methylxanthines when compared to your average milk chocolate or dark chocolate bar.
It takes much more white chocolate to cause methylxanthine toxicity in dogs, however, it is still very unhealthy for your dog. White chocolate is rich in saturated fats (cocoa butter and dairy) and full of sugars.
This can lead to a host of health issues ranging from teeth decay, gum disease, obesity, pancreatitis, diarrhea, and diabetes. I
t is, therefore, true that your dog eating a bar of white chocolate shouldn’t be a cause for panic but white chocolate should never be something that is voluntarily given to your dog. 
What should I do if my dog eats chocolate?
We advise to take your dog to the veterinarian immediately. If taking your dog to the vet is not an immediate option we hope that the above information can help you make an informed decision on what follows next.
Use the chocolate toxicity calculator linked above; it is better to overestimate rather than underestimate the amount of chocolate your dog ate in order to make a more conservative judgment on what should follow next.
Our advice is to keep a close watch on your dog for the next 24 hours. Provide your dog with plenty of water to drink and give them more (appropriate) food to further slow down methylxanthine absorption. This allows your dog to metabolize the toxins without being overwhelmed by them.
Giving your dog activated charcoal tablets every 12 hours will also help reduce methylxanthine absorption.
If taken to the vet immediately after the incident, the vet might decide to induce vomiting.
Do not try to induce vomiting yourself as you can harm your dog in the process. 
Also, make sure that your dog is not developing any of the above-mentioned symptoms. If at any stage your dog starts showing cardiac or nervous signs they should be rushed to the nearest veterinary clinic or hospital.
Veterinarians have the necessary medications to stabilize and manage your dog’s condition and help them recover safely.
The bottom line
While it is true that death caused by chocolate poisoning is rare in dogs, this doesn’t mean that this situation shouldn’t be taken seriously.
Sometimes, you won’t notice that your dog is suffering from underlying health issues and you learn about them by chance.
Chocolate poisoning, when not fatal, can still make your dog go through a great deal of pain and suffering and can leave your dog with permanent health issues. Always ask for a veterinarian’s opinion when your dog has eaten chocolate.
Did you know that in addition to chocolate, there are many other foods that can poison dogs? Check out our list of 31 Toxic Foods That Dog’s Should Avoid.