Marvelous Melatonin for Dogs

Melatonin for dogs? You’re probably familiar with melatonin as a common over-the-counter sleeping aid for humans with sleep-wake disturbances or jet lag. But did you know this incredible hormone also has benefits for our canine friends? In part one of this three-part series on melatonin for dogs, integrative veterinarian Dr. Julie Buzby answers your questions: what is melatonin, is melatonin safe for dogs, what are the pros and cons, and more.

How melatonin helped calm a rescue dog

Several years ago, my family adopted our dog, Zeke, from animal control. He was a shy, black mutt whose haunting eyes conveyed a checkered past. This was our second time adopting a shelter dog. Many of the challenges were the same with Zeke as with our first dog—housebreaking, learning to walk on a leash, and crate training. The latter proved to be more difficult than I’d anticipated, but we persevered with positive training.

One night, when everyone in our family was whining, including our beloved Zeke, I gave my dog melatonin to settle him. It was the turning point in our dog’s relationship with his crate.

Despite the fact that Zeke was now living his best life, his history left him with some anxiety issues, especially with regard to separation anxiety and confinement. Understandably so! As a veterinarian, I wouldn’t necessarily reach for melatonin as a first-line treatment for more severe anxiety issues in dogs, but for Zeke it was enough to “take the edge off.” Melatonin let him realize his crate was a safe space.

My own dog’s success story prompted me to research and share all the marvels of melatonin, and its many uses in both humans and our pets. Let’s take a look at how it might help some of our canine companions. (And for further discussion, see parts two and three in this series: Can I Give My Dog Melatonin? and Canine Cognitive Dysfunction and Melatonin.)

What is melatonin?

Melatonin is a naturally occurring hormone—an incredible one, at that—that is produced by the pineal gland in the brain of humans and many animals including dogs.^1,2,3,4,5,6 The pineal gland is responsible for managing sleep-wake cycles (AKA our circadian rhythm) in humans.⁴

Other organs such as the eyes, skin, bones, gastrointestinal tract, platelets, and thymus all produce melatonin, but to a much lesser degree than the pineal gland.⁵ Melatonin is created during the process that converts tryptophan to serotonin, a chemical in the brain associated with happiness.^3,6

Melatonin is produced in response to exposure to darkness. ^1,3,6 For example, levels of melatonin are ten times higher at night than they are during the day.⁶

The seasons also affect melatonin production, with overall melatonin levels starting to rise in the autumn as daylight grows shorter and achieving peak levels at the longest day of the year, the winter solstice.³ After melatonin is produced, it crosses the blood-brain barrier and enters the body and cerebrospinal fluid (CSF).⁶

As an aside, exposure to light at night blocks the production of melatonin. This has been shown to cause sleep disturbances in people who use electronics that emit light at night. Researchers have found that light from electronic devices can block the release of natural hormone melatonin at night.

Is melatonin safe for dogs?

The good news is that melatonin is incredibly safe for many dogs. Overall, it remains in the body for a very short period of time. The half-life of melatonin is only 18.6 minutes in the dog, which means it is rapidly cleared from the body.⁵ It’s usually fully cleared within 24 hours.

However, there are two important exceptions. Melatonin may cause insulin resistance, so I try to avoid it in my diabetic canine patients. Also, because melatonin is metabolized in the liver and eliminated through the urine and feces, caution is advised for dogs with liver disease or dysfunction.^4,5,6 

Along the lines of safety, it’s important to call out that, unlike prescription medications, melatonin is considered a dietary supplement. Therefore, it is not regulated by the FDA. Unfortunately, without FDA regulation, we can see variability in some nutraceuticals—melatonin is no exception. Make sure you’re buying a brand of melatonin that is well-known and trusted by your veterinarian.

Is human melatonin safe for dogs?

Generally speaking, as a veterinarian, I consider human melatonin safe for dogs. The big exception to this is melatonin gummies. Some gummies contain the sweetening agent xylitol, which is harmless in people but incredibly toxic to dogs.

Beware of xylitol in melatonin supplements

Most importantly, pet parents should avoid formulations of melatonin that contain xylitol (sometimes called birch sugar). While melatonin itself is very safe, xylitol is HIGHLY toxic to dogs. For more information about the dangers of xylitol, please read my article: Xylitol and Dogs. (Your dog is counting on you to keep him or her safe from this poison in your pantry.)

Potential side effects of melatonin in dogs

In dogs, side effects of melatonin are typically minimal, but any medication or supplement can have potential side effects. I recommend speaking with your veterinarian before giving your dog a melatonin supplement (or any supplement), even if it is an over-the-counter medication.

Here are some possible side effects of melatonin in dogs:

• Drowsiness—Because melatonin is the hormone responsible for sleep, drowsiness is expected. 
• Effects on reproductive hormones—Because melatonin is a hormone, it may demonstrate effects on reproductive hormones.^3,4
• Interactions with other medications—Melatonin may also interact with some of your dog’s other medications. If your dog is on medication or a sedative for treating anxiety, melatonin may cause an increase in the side effects such as drowsiness or lethargy.⁴ Melatonin may also decrease the effectiveness of certain blood pressure medications.⁵

With that said, one of the veterinary pharmaceutical handbooks advised treating dogs who had eaten a large quantity of melatonin by pumping the stomach.⁵ However, the reason they advised pumping the stomach was not because of the toxic effects of melatonin. Rather, it was to prevent a “stone” from forming in the gastrointestinal tract from the inactive ingredients used in the tablets.⁵ You know it’s a safe medication when the reference guide is more concerned about the tablets creating a “foreign body” than the drug itself!

A note about the use of melatonin in dogs with seizures

Melatonin has been shown to have both anticonvulsant and proconvulsant properties in humans and laboratory animals. Anecdotally, the same seems to be true of dogs. Some veterinarians reported that starting melatonin for another issue (e.g., seasonal alopecia) in dogs with a history of seizures may have increased the dog’s seizure frequency. However, others felt that it may have helped control their patient’s seizures (in combination with other anti-seizure medications).

It is hard to know for sure what, if any, relationship melatonin has on seizures since seizures are a complex entity. Thus, if your dog has a history of seizures, it is best to talk to your vet before starting melatonin.

What are the kinds of melatonin for dogs?

A quick online search will turn up dozens of options of melatonin supplements for dogs, in addition to the over-the-counter formulations geared toward humans. Like any over-the-counter medication, however, it’s important to make sure that the amount of melatonin given is appropriate and safe.

There are various forms of melatonin supplements, for both humans and dogs—capsules, tablets, chews—they even make liquid melatonin for dogs! “Regular” melatonin (not the extended release formulations) seem to be best for dogs. This is the case because the extended release products created for humans may pass through your dog’s GI tract too quickly to release all the melatonin, making them potentially less effective or variable in their efficacy.

The type of melatonin supplement you choose can be based on the size and temperament of your dog, the condition you’re treating, as well as cost. For example, if your dog isn’t tolerant of tablets, one of the liquid forms may be easier to administer. Talk to your vet about which type or brand he or she recommends for your dog.

What conditions is melatonin used for in dogs?

As mentioned, melatonin has been used in humans who have trouble falling and staying asleep or who are adjusting to time changes associated with jet lag.¹ Also, there is evidence that melatonin may help with some autoimmune conditions.¹

Interestingly, this “hormone of hibernation” may be a sleep aid and more. Melatonin may be helpful in managing many medical conditions in dogs.^1,3,4,5  Melatonin may help treat:

Altered sleep cycles and wake cycles associated with dog dementia — Because my current veterinary practice primarily serves senior dogs, I routinely recommended melatonin supplements for “doggie dementia.” Some older dogs’ sleep and wake cycles get off track, they can suffer from anxiety, etc. For more on melatonin supplements and doggie dementia, please read my article on canine cognitive dysfunction in dogs.

Altered sleep cycles and wake cycles associated with blindness in dogs — Because melatonin production increases with darkness, blind dogs may not have adequate production without the visible light/dark cycles. Giving supplemental melatonin may help balance these levels out and help blind dogs sleep through the night more consistently.

Immune-mediated thrombocytopenia — Although there is very little information on this in veterinary medicine, there have been human case reports of melatonin being useful for immune-mediated thrombocytopenia (IMTP). The precise mechanism is not yet well understood, but melatonin may increase platelet production. Increased numbers of platelets may potentially help prevent excessive bleeding in dogs with IMTP.

Alopecia (hair loss) — This is another condition where the way in which melatonin can be helpful is not well established. Some dogs experience seasonal alopecia, where their hair thins or falls out during the winter months when days are shorter. Just like it can help level out seasonal disturbances in circadian rhythm, melatonin supplements can help to lessen the effects of seasonal alopecia in dogs.

Anxiety (including separation anxiety) — One of the effects of melatonin is a reduction in the brain chemical dopamine. Too much dopamine can lead to anxiety. Reducing dopamine levels can improve signs of anxiety, particularly separation anxiety, in some dogs. There are many options for treating canine anxiety, including environmental enrichment, medications, supplements, and others. This is another area where I strongly encourage you to talk with your vet before starting a course of treatment. You can work together to determine the best treatment plan for your dog.

Cancer — Melatonin may have anti-cancer properties, particularly in estrogen-related cancers, such as mammary cancer in dogs. Melatonin can interfere with cancer cells’ estrogen receptors, and can reduce tumor growth in some cases.⁹

Atypical Cushing’s disease — Cushing’s disease in dogs (hyperadrenocorticism) is caused by overproduction of cortisol by the adrenal glands. Melatonin inhibits certain enzymes and can decrease cortisol levels. One of the symptoms we commonly see in dogs with Cushing’s disease is hair loss; melatonin can be beneficial for hair regrowth just like in dogs with seasonal alopecia.

I’d like to give my dog melatonin. What dosage can I give?

If you think your dog has a condition where he or she would benefit from melatonin, please speak with your veterinarian. Melatonin supplements are safe in the vast majority of dogs, but it is always a good idea to make sure the supplement will not interact with any other medications your dog might be taking.

If your vet feels that your dog is a good candidate for melatonin supplements, he or she will recommend the correct dosage.

What are the pros and cons of melatonin for dogs?

To summarize, there are many pros and few cons of melatonin for dogs.

PROS	CONS
Can help treat a number of conditions: dementia, anxiety, hair loss, cancer, and maybe others	Can cause drowsiness
Large margin of safety in dogs	May cause drug interactions with certain other medications
Inexpensive	Can cause insulin resistance in diabetic dogs
Comes in a variety of formulations	Certain formulations contain xylitol, which is not safe for dogs
Does not require a prescription	Not FDA regulated so there may be variability
Few and generally mild side effects
Short acting
Widely available

Marvelous melatonin

I had never thought about using melatonin the way I did with my dog that night. Zeke’s success prompted me to spend quite a bit of time researching this marvelous hormone. I was stunned by all the research studies I found that referenced melatonin for treating a variety of medical conditions. If you’re interested in taking a deep dive into the marvels of melatonin, you can find my sources below.

Whether your dog’s feeling anxious or your grey-muzzled companion needs nighttime rest, take stock in melatonin—the miracle hormone.

What questions do you have about melatonin for dogs?

Please comment below. We can all learn from each other.

Sources:

1. Byers, C G. “Just Ask the Expert: Is There a Role for Melatonin in Dogs and Cats with IMHA?” DVM360, 27 July 2017, veterinarymedicine.dvm360.com/just-ask-expert-there-role-melatonin-dogs-and-cats-with-imha.
2. Jeromin, A M. “Seasonal Affective Disorder Can Be Culprit for Canine Hair Loss.” DVM360, 1 Apr. 2003, veterinarynews.dvm360.com/seasonal-affective-disorder-can-be-culprit-canine-hair-loss.
3. “Melatonin and Seasonal Alopecias.” Veterinary Practice, 1 Nov. 2013, veterinary-practice.com/article/melatonin-and-seasonal-alopecias.
4. “Melatonin.” Plumb’s Veterinary Drug Handbook, Veterinary Information Networm, 1 Jan. 2015, www.vin.com/members/cms/project/defaultadv1.aspx?id=4692338&pid=451&.
5. “Melatonin.” VIN Veterinary Drug Handbook, Veterinary Information Networm, 30 June 2017, www.vin.com/members/cms/project/defaultadv1.aspx?pId=13468&id=7868548.
6. “Melatonin: Side Effects, Uses, Dosage (Kids/Adults).” Edited by L Anderson, Drugs.com, 26 Mar. 2019, www.drugs.com/melatonin.html.
7. Reiter, R J, et al. “Melatonin, a Full Service Anti-Cancer Agent: Inhibition of Initiation, Progression and Metastasis.” Int J Mol Sci, vol. 18, no. 4, 2017, doi:10.3390.
8. Rosenthal, M. “When Pets Lose Their Sense Of Place.” Veterinary Practice News, 9 July 2013, www.veterinarypracticenews.com/when-pets-lose-their-sense-of-place/.
9. Lopes, J R, et al. “Evaluation of melatonin treatment in primary culture of canine mammary tumors.” Oncol Rep, vol. 33, no. 1, 2015, doi:10.3892.