How Much Chocolate is too Much for a Dog, and How to Tell

Patty Khuly, DVM
January 03, 2011
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Last week’s case was not unusual for this time of the year. When big boxes of assorted chocolates abound, it’s inevitable that some dog, in some household, somewhere, will sniff it out before it’s secreted away to the designated, dog-proof zone. This means I get to handle large volumes of chocolate vomit at least once during the holiday season.

Disgusting stuff, to be sure. And you’d think it’d be enough to put a girl off chocolate forever. Except that it’s not. Chocolate is too damn good.

How good?

Enough so that some dogs want to eat it back up, even as they’re under the spell of powerful emetics like hydrogen peroxide, ipecac, and apomorphine. Enough so that even I think the gooey cow-patties of vomitus that dot the exam room smell good.

But enough of the nasty stuff. Unlike other posts I have written on chocolate toxicity (there have been at least a couple over the years), this one is more to do with knowing how much chocolate is too much.

Onto the test case, last week’s tale of two chocolates: Consider one five-pound box of mixed solid chocolates ("dark" and "milk"). Consider, also, one very silly and very fat chocolate Labrador retriever who ate all but perhaps the last half pound or so of this ill-placed (but wrapped) gift before his foil-a-flying, chocolaty-gorge-a-rama was so rudely interrupted by an invective strewn commotion on his behalf.

"I’m going to KILL Aunt Millie for sending us that box! What was she thinking?" Or something like it, was what the Lab’s owner kept muttering.

Meanwhile, we were busy a) inducing vomiting; and b) trying to figure out exactly how much chocolate he might’ve have consumed.

Sure, the box was in hand (pet owners are always told to bring in all packaging materials whenever any sort of known poisoning has occurred), but chocolate toxicity is seldom straightforward when it comes to knowing the exact dose of chocolate the dog has ingested.

Why? Because chocolate as we know it comes in many different preparations, most of which include anywhere from zero percent to nearly 100-percent cacao (chocolate’s main ingredient).

What is zero percent chocolate? That’s the white stuff. It’s made of the fatty solids in the cocoa bean and none of the poisonous compounds. What we know of as "white chocolate" is mostly cocoa butter and sugar mixed with milk. Hence, it’s 100-percent safe for dogs.

Chocolate made with 85 percent cacao and above is another story. Of all the chocolates, this variety has the highest proportion of the toxin theobromine in it (and also the highest amount of caffeine, which, while less toxic than theobromine, can add up). It tends to be marketed as "unsweetened," as plain cocoa powder, or even as cocoa beans.

Milk chocolate ranges anywhere between 20 and 60 percent cacao. What we in the States call "milk chocolate" (the ingredient in M&Ms and Hershey bars, for example) is at the lower end of this range, while what Europeans call "milk chocolate" is closer to the higher end, and maybe a bit more. The Euro version is more akin to what we might call "semi-sweet." Which can be confusing, because the difference between 20 and 60 is huge when it comes to calculating the dose your dog has received. And this disparity can mean the difference between life and death if aggressive treatment isn’t immediately undertaken.

Semi-sweet and bittersweet are closer cousins, usually somewhere between 50 and 75 percent cacao. Delicious stuff, but deadlier. Here’s what you get with choc tox:

•  Central nervous system stimulation (hyperactivity, seizures)
•  Cardiovascular stimulation (rapid heart rates and dangerous arrhythmias)
•  Increased blood pressure (relatively mild, usually)
•  Nausea and vomiting
•  Diarrhea

The difference between the more severe signs (the first two) and less severe signs (the last three) is very dose-dependent. Hence, why we MUST ascertain how much of it has been consumed, if at all possible, so we know what to expect and what degree of monitoring will be required of our patient.

After all, we don’t pull out all the stops for an 80-pound Doberman who’s just eaten half a box of chocolate cookies. He might have some diarrhea but not much more. A five-pound Chihuahua who’s consumed a four-piece Godiva truffle sampler, however, is almost certainly going to need induced vomiting, activated charcoal, IV fluids and round-the-clock monitoring on a continuous EKG, so that if his heart rate starts doing the zooms we know whether to administer anti-arrhythmia drugs or not.

Luckily, there are chocolate toxicity calculators available that even a layperson can use in the event their dog has committed the sin of chocolate ingestion. Check out this one at National Geographic, for example.

These calculators are typically based on these two assumptions:

1. The amount of theobromine per ounce of chocolate by type (according to the Merck Veterinary Manual):

•  Dry cocoa powder = 800 mg/oz
•  Unsweetened (Baker's) chocolate = 450 mg/oz
•  Cocoa bean mulch = 255 mg/oz
•  Semisweet chocolate and sweet dark chocolate is = 150-160 mg/oz
•  Milk chocolate = 44-64 mg Theobromine per oz chocolate
•  White chocolate contains an insignificant source of methylxanthines


2. The toxic dose of theobromine (and caffeine) for pets is 100-200mg/kg.

Using a calculator like the one linked above will give you a rough estimate of what to expect.

Nonetheless, we’ve already established that assumption No. 1 can be tricky depending on the type of chocolate ingested, and for No. 2, the ASPCA’s Poison Control has reported significant signs of toxicity at a much lower rate for some individuals (as low as 20 mg/kg). Hence, why caution is urged and a veterinarian’s (or Animal Poison Control’s) confirmation is strongly recommended for all but the most obvious low-dose cases (one M&M will not seriously harm even the teensiest Chi).

So what happened to my patient? Let’s just say that after many huge piles of ooey-gooey vomit, a tarry meal of charcoal and a night in the ER on fluids means that "Aunt Millie" is persona non grata in the aforementioned silly Lab’s household. Indeed, any future gifts from her may go straight into the trash — which is probably where this one belonged.

Dr. Patty Khuly

Pic of the day: OMG! PANIC! get it in my belleh!!!!! by amy_is_picnoleptic