Melatonin for Dogs: Dosage Chart & Overdose Side Effects

Dog Melatonin Dosage and Overdose
What is the right dosage of melatonin to give a dog for anxiety and sleep?

Melatonin is a hormone that is naturally produced in the body by the pineal gland located in the brain. Peak production of the hormone happens at night. Therefore, melatonin has been extensively studied and proven to be helpful in regulating sleep. But can you give it to your dog to help him sleep?

Melatonin is used in dogs for treatment of anxiety, sleeplessness, depression, and phobias. Its dosage is based on the dog’s weight in general as follows: 1 mg for less than 10lbs, 1.5mg for 11-25lbs, 3mg for 26-100lbs and 3-6mg for dogs weighing above 100lbs. An overdose usually produces side effects such as difficulty in breathing and shortness of breath.

Always see a veterinarian for a prescription and correct dosage.

Below, I will delve deeper into the uses, dosage guidelines, side effects and safety of using melatonin to manage some health conditions in dogs.

Can you give a dog melatonin?

Yes. You can give melatonin to dogs to manage anxiety and sleep disorders. It also helps in managing stress and fear. Although the drug is sold over the counter, it is advisable that you consult a professional such as your veterinarian before you decide on giving your dog melatonin.

There is a lot that can go wrong with any drug since there are allergies, interactions etc. to worry about before administering it to Fido.

Is it safe?

Although the FDA has not approved its use in dogs, the side effects of using melatonin are very rare when given in the right dosages.

It is important to know that a melatonin supplement preparation that contains Xylitol is NOT SAFE for dogs. Xylitol is highly toxic to dogs and can produce severe side effects such as dizziness, vomiting, wobbling and even seizures.

As with all medications, the severity of side effects depends on the dose administered and the interaction between melatonin and certain other medications given to your dog.

Your veterinarian should be aware if your dog has been previously on any medication or is currently undergoing therapy with any drug.

Uses of melatonin for dogs

Melatonin has a variety of uses in dogs. The major uses are for treating and managing teh following canine problems:

  • Anxiety
  • Depression
  • Phobias/fear
  • Sleep
  • Physiology function
  • Role as an antioxidant
  • Role in the immune system
  • Dietary supplement
  • Reproductive role

These uses are dose-dependent; hence, an expert should always be consulted before initiating therapy.

Melatonin for insomnia in dogs

Canine insomnia is a problem that can change your dog’s personality. According to Dr. JoAnna Pendergrass, DVM, dogs with sleep disorders might whine, cry, or frequently wake up during the night, become more sluggish during the day or seem more disoriented when performing normal tasks.

Melatonin is not the major regulator of sleep patterns. However, its effects on the regulation of the sleep-wake cycle are profound.

The role of melatonin in the regulation of sleep has made it useful in treating sleep disorders. This action is well documented in humans; however, more studies are still being done in animals. When administered to your dog, melatonin will cause decreased activity, decreased body temperature and eventually induce fatigue. In this regard, an appropriate dose of melatonin may be used to induce sleep in a dog suffering from sleeping disorders.

Melatonin Reduces Anxiety

Serotonin, the precursor of melatonin, has always been known to improve mood and enhance a positive feeling. This happens when there is an increased amount of serotonin in the brain due to inhibition of its reuptake by cells.

Similarly, melatonin has some documented actions of reducing anxiety. When administered, melatonin mimics certain mood enhancement effects reminiscent of the action of serotonin.

Dosage: how much melatonin can you give a dog?

Here’s dosage chart based on weight.

Dog’s Weight Melatonin Dosage
10 lbs 1mg
11 to 25 lbs 1.5mg
26 to 100 lbs 3mg
Over 100 lbs 3 – 6 mg

Melatonin for dogs is available over the counter. However, you should always consult your veterinarian to help you determine the right dosage for your dog.

Individual dogs are given different dosages based on their difference in body size and the type of condition being managed. This means that the amount required to induce sleep in sleeping disorders may differ from the amount used to treat anxiety and fear.

Your veterinary will weigh your dog to determine his/her weight. The weight obtained will then be used to calculate the melatonin dosages for your dog with reference to the condition being managed.

Ideally, 1 mg of melatonin is the recommended dose for dogs who weigh less than 10 pounds. This is the average amount of drug that should be given to avoid complications. Dogs weighing 10 to 25 pounds are managed with a dose of 1.5mg while dogs weighing 26 to 100 pounds are managed with a dose of 3mg.

Additionally, 3 to 6 mg is recommended for dogs weighing more than 100 pounds. Some dosages may exceed these limits since these are the standard amounts for melatonin therapy in dogs.

Nevertheless, you should seek guidance from a qualified expert such as your veterinary officer to avoid the possibility of overdosing or underdosing your dog. These dosages are indicated each for a single use and should not be administered more than three times within 24 hours.

Melatonin is available in different formulations. It can be bought as a tablet, powder, liquid or capsule. The formulation you choose to use depends on ease of administration and your preference. The powder can be mixed with food or water before administering to your dog while tablets and capsules should just be given for the dog to swallow. These directions are always given as instructions from the chemist or from the veterinarian.

It is also safe to administer melatonin before or after feeding your dog. The onset of action of melatonin is about 10 to 15 minutes after oral administration. Its effects in the body can last for as long as 8 hours when the dosages are administered in correct amounts as prescribed by the veterinarian.

The longer duration of action is the reason why it is mostly used to ensure that dogs have a good night sleep.

Dog melatonin overdose

Melatonin overdose in dogs occurs when the prescribed dosage is not adhered to or when you accidentally give more drugs than expected. This is common to liquid and powder formulations of melatonin.

An overdose may also imply that the dose prescribed for your dog by the veterinary officer is too high and should, therefore, be reduced.

Side effects may be more severe in dogs that are pregnant since melatonin is not appropriate for use during pregnancy.

It is, however, difficult to determine melatonin overdose since there is no official standard dose that has been set for every dog. The symptoms and their severity are the surest way of determining if there is any possibility of melatonin overdose.

It is very important to read the instructions labeled on melatonin before purchasing them. Some of these medications are artificially sweetened by substances that could be toxic to dogs.

The most commonly used artificial sweetener is xylitol and is very toxic to dogs. It is true you might be doing well to help combat anxiety and fear in your dog. But you should be careful not to poison your lovely dog when trying to help him or her.

Additionally, some medications interact with melatonin when administered together. This interaction may worsen the dog’s condition or cause more adverse reactions in the body.

You should always remember to inform your veterinary officer any medications you are giving your dog. The veterinarian will then determine whether to stop those medications or prescribe different drugs.

The veterinarians will also advise you on the best melatonin supplements to use. You may also have to decide whether to use supplements or not.

What to do in case of an overdose?

Management of melatonin overdose usually depends on how severe the condition is. The most severe manifestation of melatonin overdose is shortness of breath and difficulty in breathing.

The first thing to do in the event of an overdose is to take your dog to the veterinary officer without delay to receive prompt treatment.

If your dog is so overwhelmed that his/her breathing is failing, the veterinarian will first focus on making the dog stable before commencing any further treatment.

Once the dog is stable, it is advisable to stop the use of melatonin immediately. There are no documented effects of stopping treatment with melatonin abruptly and therefore no complication should arise due to a sudden stop in treatment

If the overdose is not severe, you only need to stop administering melatonin.

Side effects may also be caused by toxicity which have nothing to do with an overdose. In this regard, never use melatonin with artificial sweeteners in the ingredients. You will also have to take your dog to the vet for the removal of toxins and further health assessment.

Side effects

One good thing about melatonin for dogs is that the side effects are very rare and uncommon. Even if they occur, the symptoms may not cause any serious complications.

Side effects are only rare and less complicated if the right procedure is followed when administering the medication. The right amount of dosages as prescribed by the veterinarian should also be adhered to.

Most of these side effects are consistent with overdose. However, depending on the body chemistry and the size of your dog, some side effects can occur after administering melatonin.

These side effects include:

  • Stomach upset.
  • Abdominal cramps.
  • The dog may be confused.
  • The dog’s skin may start getting itchy.
  • The dog’s heart rate may increase abruptly – a condition called tachycardia.
  • Melatonin overdose can also cause changes in your dog’s fertility.
  • Diarrhea may occur.

Besides these side effects, melatonin can also worsen symptoms of some preexisting conditions. These conditions include:

Dogs with bleeding disorders

If your dog has any bleeding disorders, melatonin overdose can worsen the condition leading to severe loss of blood and anemia. This can make your dog vulnerable to attack by diseases ultimately leading to a deteriorated health.

Dogs suffering from episodes of seizure

If your dog is prone to seizures and is being managed, melatonin overdose can increase the occurrence of the seizures making it hard to manage.

Interestingly, melatonin can be used to manage seizures in dog. Like most anti-seizure drugs, melatonin is only profitable in right amounts. An overdose may worsen the disease. You certainly don’t want to subject your dog to seizures after trying your best to manage the condition.

Your veterinarian will help you manage anxiety in dogs with seizures.

Immunosuppressive drugs

Your dog may be treated with immunosuppressive drugs due to some underlying diseases of the immune system. However, melatonin overdose can interfere with such therapy since melatonin interacts with some immunosuppressive drugs.


Melatonin can increase blood sugar levels in dogs suffering from diabetes. Increase in blood sugar levels in diabetes is a dangerous state and can easily lead to deadly complications.

Dogs suffering from diabetes should not be given melatonin to prevent such complications from arising.

How does melatonin work for dogs?

To better understand how melatonin works, it is important to find out the natural process of how melatonin is synthesized and how it works.

Production of melatonin: Melatonin is synthesized in three major sites of the body;

  • Pineal gland – A glandular nervous tissue that protrudes in the region of the brain called mid-brain behind a very important structure of the brain called superior colliculi.
  • RetinaThe retina, a layer of tissue located behind the inside part of the eye next to the optic nerve, also produce melatonin.
  • Gastrointestinal tract Studies have shown that the gastrointestinal tract produces more melatonin compared to the pineal gland. The amount produced is estimated to be about 500 times more than the amount produced by the pineal gland.

The principal source of melatonin is dietary tryptophan, one of the essential amino acids required by the body. Tryptophan is also a precursor for the synthesis of serotonin.

Synthesis and regulation

Naturally, the synthesis and release of melatonin are regulated by the amount of light entering the eye. This means that, during the day or in the presence of light, you can detect little to no levels of melatonin in blood.

However, when the eyes are closed such as at night when trying to sleep, melatonin reaches peak production levels. This literally explains the relationship between melatonin and sleep regulation.

Serotonin, which is the precursor for forming melatonin, is synthesized from the amino acid tryptophan. In the pineal gland, a series of enzymes convert serotonin to melatonin through the chemical processes of adding an acetyl and a methyl group. These processes are called acetylation and methylation respectively.

How it works: Melatonin receptors are available in the membranes of body cells. At the cellular level, melatonin has the following functions.

Effects on reproduction

Melatonin is physiologically anti-gonadotropic. This means that it acts by inhibiting the secretion of reproductive hormones such as luteinizing hormone and follicle stimulating hormone. These hormones are usually produced in the pituitary gland and act in the reproductive system to regulate the breeding cycles.

Melatonin can be used in female dogs to manipulate breeding cycles depending on whether you require puppies off from your dog or not. This mechanism of action is the natural regulator of breeding cycles in most animals depending on the prevailing climatic seasons.

Other physiologic functions

 As an antioxidant: Antioxidants alleviate oxidative stress in cells by helping in removing reactive molecules of oxygen. Melatonin being an antioxidant prevents damage to DNA, nucleus of the cells and mitochondria. In this regard, it also helps in preventing certain cancers from developing.

Role in the immune system: Based on its antioxidant properties, melatonin boosts the role of immune system in the attack against pathogenic organisms.

It also stimulates the production of immune mediator cells called T-lymphocytes. These cells are one of the major mediators of the immune response against invading pathogens such as bacteria, viruses, parasites, and fungi.

Dietary supplement for dogs: In the right amounts, melatonin can be added as dietary supplements to alleviate stress for the body in synthesizing bio-molecules from tryptophan.

Most of these functions of melatonin are still under study. Therefore, its use for whatever reason should be carefully monitored and regulated to prevent the occurrence of any unprecedented side effects.

Other medications used to treat anxiety in dogs

Other than melatonin, drugs used to treat anxiety in dogs include:


This is a tricyclic antidepressant associated with anticholinergic effects, mild sleepiness and effects on the gastrointestinal system. It is given in a dose range of 1-3 mg/kg.


Clomipramine is also a tricyclic antidepressant that causes transient lethargy and vomiting. It should be given with food because the gastrointestinal effects are more severe on an empty stomach. It is given in 1-3mg/kg dosages.

Clomipramine is the most commonly used drug to treat anxiety in dogs. Its brand name is Clomicalm. It acts by blocking the reuptake of serotonin thereby increasing the levels of serotonin in the brain.

Increased levels of serotonin helps in reducing stress, fear and anxiety experienced by your lovely dog.


This is a serotonin reuptake inhibitor. It causes decreased appetite and transient lethargy. It is also not advisable for use in seizures. Fluoxetine is administered in dosages of 1-2 mg/kg.

Other medications such as diazepam, lorazepam and clorazepate can also be used to manage anxiety in dogs since their effects are almost similar to the aforementioned drugs.


The following are some frequently asked questions about using melatonin for dogs.

How long does it take for melatonin to work for a dog?

Melatonin takes about 10 to 15 minutes to start manifesting its effects. This is called the onset of action. Blood levels of melatonin will remain elevated for up to 8 hours.

For this reason, it can be efficiently administered when the dog is about to sleep to enhance a good night sleep.

Can overdose kill a dog?

The severity of symptoms due to melatonin overdose depends on the size of the dog and the amount of exposure to the drug.

A severe overdose can lead to the depression of breathing which can ultimately cause death if not managed. However, most cases of melatonin overdose in dogs resolve on their own when the medication is stopped and cannot kill a dog.

It also difficult to overdose your dog on melatonin since the dosage is regulated and there is no clearly defined limit that can cause an overdose.

Can I give my dog Benadryl and melatonin at the same time?

Benadryl and melatonin are synergistic in their actions and therefore should not be used together in dogs. Synergy means that when both the drugs are administered together, they augment the action of each other such that the overall effects of the two drugs combined are greater than the sum of individual effects.

This overall effect may be similar to melatonin overdose and could cause side effects consistent with an overdose.

Seek more information about the appropriate drugs to use in conjunction with melatonin when treating your dog.

Melatonin is very much safe for use in the management of anxiety, fear and sleep disorders. The side effects are very rare making it more appropriate and safer than other medications that can be used for similar purposes.

You should always seek expert advice when you are considering the use of melatonin to manage any condition to prevent worsening of any preexisting conditions.

Ideally, it is not advisable to self-diagnose your dog and start administering medications. If your dog’s health is worrying you, you should talk to your vet and get expert help.

The prognosis for anxiety, fear and sleeping disorders after treatment with melatonin is usually good. Save your dog from anxiety and fear by choosing the best treatment option for him or her.



  1. Journal of the American Veterinary Medical Association, Volume 215, No. 1 July 1999. Vet Med Today: Animal Behavior Case of the Month, written by Linda Aronson, DVM, MA; from the Department of Clinical Studies, School of Veterinary Medicine, Tufts University, North Grafton, MA.
  2. Wetterberg, L., Eriksson, O., Friberg, Y., Vangbo, B.A simplified radioimmunoassay for melatonin and its application to biological fluids. Preliminary observations on the half-life of plasma melatonin in man. Clin. Chem. Acta86, 169 –177 (1978).