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Featuring Demian Dressler, DVM and Sue Ettinger, DVM, Dip. ACVIM (Oncology), authors of The Dog Cancer Survival Guide

More Melatonin and Dog Cancer

Updated: April 13th, 2021


More details on melatonin and dog cancer, including the whys, hows, and how much.

You want more on melatonin and dog cancer? You just hit the jackpot!

Why Melatonin?

Why should we be interested in this weird body hormone that is only generated in complete darkness?  Lots of reasons.

First of all, melatonin used with chemo versus chemo alone more than doubled the survival time of human cancer patients. That’s a big effect, folks.

Secondly, in that same study, melatonin decreased the side effects related to chemotherapy.  These included low platelet counts, irritations of the lining of the mouth (stomatitis), nervous system injury (neurotoxicity), and heart toxicity (cardiotoxicity).  Again, that is huge.

Listen to this episode of Dog Cancer Answers to find out more about how to use melatonin to fight dog cancer. 

A simple hormone, produced naturally, and also cheaply found in supplement form, is related to doubled survival times and decreased side effects? That’s literally a no-brainer.

But Wait, There’s More:

Melatonin helps overcome weight loss due to cancer (cancer cachexia)  in advanced cancer patients, with no change in how much food they are eating.

As if this were not enough, a study looked at over 600 cancer patients, with a variety of solid-tissue tumors, who received melatonin.  The 1 year survival time of the group that took melatonin was more than a third greater than those that did not.

Melatonin was also the topic of a medical conference which discussed the ability of melatonin to cause some cancer cells to not only die off directly, but go back to being healthy body cells, and decrease cancer spread (metastasis). Let me restate that: melatonin seemed to not only kill cancer cells but in some cells, to turn them BACK TO HEALTHY CELLS.

To boot, melatonin is an immune stimulator.


To put it mildly, there is lots of promising stuff here.  One of the points made at that conference was that this information has been around for years — but has not made it into the medical or veterinary knowledge pool.  (As I pointed out in the last post, I think the obvious reason is that you can’t patent it, which means no pharmaceutical company is interested … but I digress.)

Free Ways to Boost Melatonin

Obviously, dogs produce melatonin at night, in complete darkness, just like humans do. That’s why it’s a good idea to increase your dog’s natural melatonin output — and possibly even supplement it.

First, the free strategies: create a natural “den” for your dog to sleep in. Total darkness, for at least 10 hours daily can be accomplished in many ways:

  • If your dog likes sleeping “under” things, like tables, or beds, let them do it. This is their way of stimulating melatonin, by seeking dark places to snooze.
  • If your dog likes to sleep in a crate, there are fantastic covers that make it super-dark in their little cave.
  • Make your bedroom a den, particularly if your dog sleeps with you. Use blackout shades on your windows, and make sure all sources of “blue light” from TV screens, computers, tablets, and phones are removed. Stop using night lights. Make your room as dark as possible, so your dog’s brain has a real shot at generating melatonin.
  • If you can, avoid charging your devices where you sleep, because electrical fields can interfere with melatonin production. For the same reason, considering unplugging lamps and other devices at night.
  • Try some fresh sage in your dog’s cancer diet — it has lots of naturally occurring melatonin!
  • Other rich sources of melatonin are brown rice and oats, both of which are optional additions to the dog cancer diet outlined in my book.
  • Meditation — yes, meditation — increases melatonin levels. Try meditating with your dog!

Supplementing with Melatonin

Dogs vary in their natural ability to generate melatonin, and they also vary in size. Therefore, melatonin doses vary, too.

If your dog is in the early stages of dog cancer, I recommend using 1-2 mg per 40 lbs body weight, once a day, given at night.

For advanced dog cancer patients closer to the end of their life, I recommend 5 mg per 40 lbs.

You can use either tablet or liquid forms, whatever works best for your dog. Whatever form you choose, give melatonin with a little food to buffer the stomach — just a snack will do it.

I like human-grade supplements because they are manufactured to stricter standards than pet-grade supplements. Melatonin is a really inexpensive supplement, and worth trying with your dog.

Side Effects for Melatonin and Dog Cancer

Here’s the skinny on side effects and whatnot…

  • Don’t give your dog melatonin during the daytime, because it messes up their circadian rhythm and causes headaches. You probably know this firsthand if you’ve ever woken up in the middle of the night and had to turn on the light only to get very groggy and a little sick.
  • Any supplement given by mouth has the potential for digestive upset (vomiting or nausea), of course, which is why I suggest giving with a little food.
  • If your dog has any immune-mediated disease (like some types of underactive thyroid problems, dry eye, lupus, pemphigus, allergies, and so on), avoid it.
  • Don’t give melatonin to your dog if he or she is on calcium channel blockers (some types of heart and blood pressure meds), or is on fluoxetine (Prozac).
  • Because melatonin can influence metabolism, diabetic dogs may need less insulin on melatonin. So if your dog has diabetes, begin melatonin only with your vet’s close supervision and instruction. If you are not willing or able to consult with your veterinarian to manage diabetes medication, please skip melatonin. You don’t want to overdose your dog on insulin unnecessarily!
  • Melatonin being generated by the brain, I would avoid melatonin as well if your dog is epileptic.

There are statements suggesting melatonin should not be used with leukemia or lymphoma patients circulating.  I have tried to find some actual evidence for these (a paper, case report, anything real) but to no avail.  Any input from the readers?

The same is true with this idea that it can cause retinal injury. This appears to be speculation, but I am open to any documented, real evidence.

Best to all,

Dr. Dressler

Leave a Comment

  1. jean brickwedde on July 29, 2009 at 1:01 pm

    Sorry, Rimadyl, not Ridilin

  2. jean brickwedde on July 29, 2009 at 1:00 pm

    I have a 13yr old spayed female Akita, diagnosed with Cushings, not yet determined if adrenal or pituitary, and has hypothyroidism, and have just started her on Ridlin for her weakening ( and I assmue painful ) hind quarter.
    Can melatonin help relieve the symptoms of Cushings, regardless of which type, and if not, why not?; and what does the hypothyroid have to do with it?
    I appreciate your answer.
    Thank you
    Jean Brickwedde

  3. Karen Bender on June 27, 2009 at 3:08 pm

    Thank you, Dr.Dressle, for your response. Mack is getting closer to the end now. I stopped the melatonin (only gave it to him for about 5 nights) and he actually slept better last night. I lowered his prednisone (initially he was on 10mg every other day until our vet raised him to 10mb bid last week.) Maybe that was keeping him up, also. He is still eating heartily, still wags his tail when I come home, and still barks at people passing the house. He is having labored breathing somewhat. I just don’t know where the fine line lies between his feeling well and actually starting to die. I don’t want it to be an emergency euthanasia, but I don’t want to do it prematuely either.
    Thank you for helping and listening,

  4. karen bender on June 21, 2009 at 2:02 pm

    Hi Doc – I understand melatonin can be taken in addition to prednisone, but what about along with PHENOBARB?

    Thank you so much,

    • Dr. Dressler on June 27, 2009 at 12:28 am

      Karen, I do not see a immediate conflict aside from excessive sedation possibly. There have been no studies though, so the use of these together has not been shown to be definitively safe. In the realm of neurotransmitter modification, nobody knows the whole real story…just not enough info yet..

  5. Karen Bender on June 14, 2009 at 4:11 pm

    Hi Doc – my Mack is an 11 yr golden with meningioma of olfactory lobe. He is on prednisone 10mg every other day and phenobarb 75mg bid. Can he take melatonin for sleep? After sleeping quite well at night since he was diag’d in Sept’08 has recently been up at night panting. His wt is 84-85lbs. How much can he take? Thank you so much in advance,
    Karen Bender

  6. Eve on February 17, 2009 at 12:32 pm

    Where did you come up with this info?
    My vet and the vets at the University of Tenn, all have put my dog on this.
    Check out Dr Oliver at the vet university of Tenn.
    He knows more about atypical cushing’s then most.
    So tell us where you got this info, what medical test have you done to prove this?

  7. Patrick B on January 14, 2009 at 7:36 am

    Hi Dr. Drexler:

    You wrote, “There are statements suggesting melatonin should not be used with leukemia or lymphoma patients circulating around.”

    I have read that melatonin also has antioxidant properties. That may be the reason for the statements. I have found that many vets, as I am sure you are aware, tell their clients to never give any antioxidants when receiving chemotherapy.

    Do you have some current thoughts on this subject?


  8. Dr. Dressler on October 5, 2008 at 3:09 pm

    1. There is not an interaction between pred and melatonin. There was a study using dexamethasone where melatonin blocked the suppression of normal immune responses (but not the suppression of cancerous white blood cells).
    2. The effects of melatonin in cushing’s is mediated by sex hormone imbalance and effects of it on hair follicles and other body systems, not by suppression of cortisol or the other corticosteroids that are in excess in typical cushings.

    Melatek markets Dermatonin, the implants.

    Dr D

  9. Lilly F on October 4, 2008 at 5:50 am

    oops, error above, I meant melatonin implants, (in lieu of oral melatonin) not patches.


  10. Lilly F on October 4, 2008 at 5:43 am

    My dog Candy was prescribed a melatonin regimen for her Atypical Cushings– meaning that her hormones were out of whack but she had normal cortisol (steroid) levels on the Tennessee Adrenal Panel. But, melatonin is also prescribed as an alternative treatment for dogs with Cushings who do have high cortisol (steroid) levels. I was giving melatonin and phosphatidylserine (to keep cortisol levels in check)
    Some are using melatonin patches in lieu of oral melatonin to deliver a supposed more reliable, even dose and some claim that it prevents daytime drowsiness. So, I guess what I am saying is that when dogs have high steroid levels (cortisol) that melatonin is being touted as in Cushings disease (high cortisol levels) to prevent panting, excessive thirst, excessive urination etc….. So does melatonin lower cortisol level or modulate it? In your case would the melatonin modulate or lower the pred, thereby canceling out the pred or have no effect. I guess Dr. Dressler will help us out here.

    Would prednisolone have fewer side effects than prednisone–I heard that on one of my lists. Also there is a compounded version of prednisone without the negative effects of prednisone but the same benefits. Best of both worlds–same positive effect, none of the negative effects. Some have used this form to reduce liver enzymes. I don’t know if this is anecdotal information or supported by studies.

    I have taken Candy off melatonin now because of some things I have read to not give it with a lymphoproliferative cancer, as in cutaneous T cell lympoma which Candy has–also called Mycosis Fungoides. I understand it has promise with organ tumors though.

    I don’t know for a fact about the interference of Pred with Melatonin but thought this info would help provide some understanding of the mechanism of action for which it is used in Cushings.


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