Help! My Dog Ate Melatonin

Many of us use melatonin supplements.

A study in 2018 found that in the US, three million adults and half a million children are taking melatonin supplements.

And as our ability to sleep probably gets worse over time, our reliance on this supplement will only increase.

But melatonin can also be prescribed for use with our dogs.

Which is a bit of a strange one since very few dogs seem to have sleep issues!

So how is it used with dogs and is it true that certain brands of melatonin could potentially harm your dog?

Those are just two of the questions that I hope to answer in this article…

What is melatonin?

Melatonin is a natural hormone, found in humans but not dogs.

It is made by the pineal gland, which is located in the brain.

The gland produces melatonin when it is getting dark outside and it continues to produce it until the early hours of the morning. 

It is a hormone that encourages us to sleep and controls how we sleep. 

Melatonin is also available as a pill

So at this point you might be shaking your head and wondering what has this got to do with dogs or, why are they eating it?

As well as being a naturally produced hormone, melatonin is available as a pill.

In the US it can be bought without a prescription and over the counter but in the UK it is only available as a prescription from a doctor.

It is prescribed to humans for three sleep related instances. 

  1. Adults (who are over 55 years old) as a way to cure short term insomnia.
  2. Children with sleeping difficulties
  3. Adults who are struggling with jet lag

It is also prescribed to some adults who get headaches and some adults who are visually impaired (because their pineal gland doesn’t produce melatonin properly.) 

Can melatonin pills be used with dogs?

Yes, melatonin is prescribed by vets to be used with dogs. 

And just like humans, in the UK you will need a prescription from your vet.

But in the US, they can be bought over the counter and this is where a lack of control can get you and your dog in trouble.  

It tends to be prescribed to dogs for three main reasons:

  1. Elderly dogs with disturbed sleep
  2. To treat hair loss (alopecia)
  3. Separation anxiety 

Melatonin is an extra label drug drug as far as dogs are concerned.

Extra label means that there isn’t a melatonin pill that has been specifically developed for use with dogs and so they pills that were developed for other species- either humans or ferrets (yes, ferrets!)

What’s the evidence?

Not surprising, there have been limited clinical trials of using melatonin with dogs. 

One of the most influential people seems to be Dr Linda Aronson who is a doctor of veterinary medicine (DVM.)

She has used melatonin with dogs and in 1999 published a study that involved using melatonin with dogs that are highly anxious. 

The original article isn’t available online and so I need to rely on other people’s summaries of the results. 

The drug was able to calm over 80% of dogs who were very fearful of fireworks or thunderstorms.

And by taking melatonin they were very calm within 15 minutes of ingesting the pill. 

What is a safe dosage of melatonin for a dog?

Not surprisingly, the size of the dose of melatonin that you can give your dog depends on the size of your dog.

Remember, you should be guided by your vet. 

Melatonin pills are given every eight hours in the following quantities:

  • Small dog (under 10 lbs) 1.0 mg 
  • Medium dog (10- 25 lbs) 1.5 mg
  • Large dog (25- 100 lbs) 3-6 mg

Are there any side effects to melatonin?

Melatonin is known to be a very safe and predictable medication for dogs. 

However, it shouldn’t be used with pregnant bitches or young dogs

It can also lead to:

  • Gastric upset
  • Increased heart rate
  • Itching and confusion

Can a dog overdose on melatonin?

Yikes! My dog has eaten most of a jar of melatonin…

Yes, a dog can overdose on melatonin but it is hard to quantify how much is too much. 

One of the reasons for this is because scientists aren’t even sure how much melatonin a person needs in order to overdose. 

Although this article roughly estimates that a melatonin overdose for a person would be three times the highest recommended dose. 

And so referring back to the dosage figures earlier, possible harmful levels of melatonin for the three sizes of dogs would be:

  • Small dog (under 10 lbs) 3 mg 
  • Medium dog (10- 25 lbs) 4.5 mg
  • Large dog (25- 100 lbs) 9-18 mg

If you suspect that your dog has overdosed on melatonin then you need to get in touch with your vet as quickly as possible or phone the Pet Poison Helpline. 

My dog has eaten melatonin with xylitol

Apart from overdosing, there is another way in which melatonin can be life threatening for your dog.

And this is when you accidentally give him a human melatonin pill which is sweetened with xylitol.

Dogs cannot process xylitol properly. 

When xylitol enters your dog’s blood stream it will cause a release of insulin which triggers a decrease in a dog’s blood sugar levels. 

And this could eventually lead to liver failure. 

The toxic level is thought to be anywhere around 50 mg of xylitol per lb of dog’s body weight. (or 100 mg per kg.)

And so for my Golden Retrievers who are about 60 lbs (30 kg), they would need to ingest 3000 mg of xylitol for it to be life threatening, which is the equivalent of 3g of xylitol. 

Xylitol is added to many melatonin pills to make them more palatable. 

And this is the real trouble with buying xylitol over the counter because you might accidentally buy a brand that includes xylitol. 

A quick look on Amazon shows that the best selling brand of melatonin pills (Natrol) uses xylitol.

Every pill contains 5mg of melatonin but it doesn’t state the amount of xylitol used in each pill. But xylitol is the next biggest ingredient used in the pills.

So it is really hard to say how many of these pills your dog would need to swallow to be xylitol poisoned. 

The good news is that the best selling children’s melatonin “gummies” doesn’t contain xylitol- they use honey as the main sweetener instead. 

The symptoms of xylitol poisoning

The symptoms of xylitol poisoning that you need to look out for are:

  • Vomiting
  • Lethargy
  • Difficulty with walking (lack of coordination.)

And needless to say that if your dog displays any of these symptoms, you should be getting in touch with your vet ASAP. 

James Grayston

My name is James and I love dogs. have owned four Golden Retrievers in the past 15 years. Currently I own two "Goldies"- a five year old and a seven month old. The photo shows me with our youngest when she was about 7 weeks old!