Melatonin Dosage for Dogs Chart: Doses by Weight in kg and mL

The melatonin dose most often quoted for dogs is about 1 mg for dogs under 4.5 kg, 1.5 mg for 4.5–11 kg, 3 mg for 11–45 kg and 3–6 mg for dogs over 45 kg, given no more than three times a day and usually about 30 minutes before bedtime or a stressful event. In the UK there is no melatonin medicine authorised by the Veterinary Medicines Directorate (VMD) for dogs, and for people melatonin is prescription-only, so there is no official UK data sheet with a licensed canine dose. Treat every number below as a starting framework, start at the low end of your dog's band, and let your vet confirm the amount for your individual dog.

In brief: weigh your dog in kilograms, find the band, convert milligrams to millilitres for the product you actually have, and never improvise with a human tablet or gummy. If your dog has already swallowed one, skip to "My dog ate 10 mg".

Melatonin dosage chart for dogs by weight (kg)

The millilitre column assumes a liquid standardised at 3 mg of melatonin per millilitre, the strength of our own melatonin drops for dogs. If you use a different product, recalculate against its label strength (the formula is below the table). For a comparison of two different calming approaches, see melatonin versus trazodone.

What the chart means for common UK breeds

Weight, not breed, sets the band, but it helps to see the chart against dogs you meet on a British pavement. Use your own dog's weight from the last vet visit or the scales at the practice reception.

• Chihuahua or Yorkshire Terrier around 3 kg: about 1 mg, so roughly 0.33 mL of a 3 mg/mL liquid.
• Jack Russell or Shih Tzu around 7 kg: about 1.5 mg, roughly 0.5 mL.
• Cocker Spaniel or Cockapoo around 13 kg: about 3 mg, roughly 1 mL — this dog has only just crossed into the third band, so it makes sense to start at the lower end and work up with your vet.
• Labrador or Golden Retriever around 30 kg: about 3 mg, roughly 1 mL.
• Newfoundland or Great Dane over 45 kg: 3–6 mg, roughly 1–2 mL; start at 3 mg.

Converting milligrams to millilitres for any product

The arithmetic is the same whatever the bottle: millilitres = dose in mg ÷ strength in mg per mL. At 3 mg/mL, 1 mg is 0.33 mL, 1.5 mg is 0.5 mL, 3 mg is 1 mL and 6 mg is 2 mL. A product made at 1 mg/mL would need 1.5 mL for the same 1.5 mg dose, so always read the strength on the label you are holding rather than reusing a number from a forum.

Expressed per kilogram, the chart works out at roughly 0.07–0.5 mg/kg: generous for the smallest dog in each band and modest for the heaviest. That spread is one reason vets start at the bottom and adjust.

Melatonin rules in the UK: why your vet sets the dose

Melatonin is the same hormone in people and dogs, but its legal position in Britain is different from what many US articles assume. The NHS states that melatonin "is available on prescription only" for people, and the brands it lists (Circadin, Adaflex, Ceyesto, Slenyto, Syncrodin) are medicines dispensed against a prescription.¹ No melatonin product is authorised by the VMD for dogs, so a vet who wants a dog to have a melatonin medicine prescribes it under the cascade, the legal route that lets UK vets use a human or unauthorised product when no suitable authorised veterinary medicine exists.²

Two practical consequences follow for the chart above:

• There is no UK summary of product characteristics (SPC) for a canine melatonin dose. Every chart you see, including this one, is clinical convention rather than a licensed label. That is exactly why the final number belongs with your vet.
• The melatonin already in a British home is usually the wrong format. It is either a family member's prescription (often a 2 mg slow-release tablet, which the NHS says must be swallowed whole and not cut or crushed) or a gummy ordered from abroad. Neither divides into a 1 mg or 1.5 mg dog dose. Our guide to whether dogs can take human melatonin covers this in detail.

Where the standard chart actually comes from

Almost every melatonin dosage chart online repeats the same four weight bands without saying where they came from. The honest answer is that they are a clinical convention passed between veterinary references and owner guides for years. We have not found a published dose-ranging trial in dogs that established 1.5 mg, rather than 1 mg or 2 mg, as the right dose for a 9 kg dog.

That is not a reason to discard the chart. What controlled data exist are reassuring on tolerance: in a randomised, blinded, placebo-controlled study, 40 healthy dogs received oral melatonin at 3 mg twice daily (under 15 kg) or 6 mg twice daily (15 kg and over) for 28 days, with no adverse effects or sedation noted and no change in platelet function (Chen and Stone, 2019).³ The Merck Veterinary Manual describes oral melatonin at 3–6 mg per dog as an empirical approach for some coat conditions.⁴ What the chart is not is precision medicine. Start at the low end of your dog's band and let your vet adjust it based on what you actually see, not on what a table says. Before attributing all the scratching to this problem, check the parasite-control side of the routine. Our flea and tick treatment comparison separates flea treatment and prevention choices from general skin-support products.

For dermatological use the picture is different again: the doses are higher, the timescale is months and the evidence is mixed. Our guide to melatonin for Alopecia X and Cushing's in dogs walks through what the trials found.

Why a small dose can do nothing at all: canine pharmacokinetics

Dogs do not absorb melatonin in a straight line, and this is the most useful thing an owner can understand about dosing it.

In a pharmacokinetic study in the Journal of Pineal Research, oral bioavailability in dogs was only 16.9% at 1 mg/kg, meaning most of the dose never reached the bloodstream, yet at 10 mg/kg the dose-normalised bioavailability exceeded 100%.⁵ The authors describe this as dose-dependent bioavailability: at low doses the liver clears much of the melatonin on its first pass, and only once that route is saturated does more of the dose get through. The same study measured an elimination half-life of 18.6 minutes after an intravenous dose of 3 mg/kg.

Two practical points follow. First, a small dog given a genuinely small dose may show no visible effect at all — not because melatonin "doesn't work on terriers", but because little of it made it past the liver. Second, because absorption is not proportional, doubling a dose is not a small tweak. If the starting dose seems to do nothing after several calm, well-timed tries, that is a conversation for your vet rather than a reason to reach for more.

Real-world timing data are thin, but one Austrian trial is useful: when 50 healthy dogs were given melatonin by mouth two hours before anaesthesia, the nervous dogs in the melatonin group were measurably calmer than those given placebo by the 90-minute mark, with vital signs staying within normal ranges.⁶ That dose (5 mg/kg) was a supervised research dose, far above the chart, and is not a home reference. For the full timeline of onset and how long the effect lasts, see how long melatonin lasts in dogs.

A dose is only as accurate as the label

Measuring to the milligram means nothing if the bottle is wrong, and two independent analyses show melatonin labels often are:

• A 2023 JAMA research letter tested 25 melatonin gummy products sold in the United States: 22 of 25 (88%) were inaccurately labelled, only 3 were within ±10% of the declared amount, and actual melatonin ranged from 74% to 347% of the label. One product contained no detectable melatonin at all but did contain undeclared CBD.⁷
• An earlier study of 31 supplements in the Journal of Clinical Sleep Medicine found melatonin content from 83% below to 478% above the label, lot-to-lot variation within one product of up to 465%, and serotonin in 26% of the products tested.⁸

Because melatonin cannot be sold over the counter to people in the UK, gummies in British homes almost always arrive from overseas websites and marketplaces — the very kind of product those studies tested. That is the case for choosing a dog product with full per-millilitre disclosure and batch testing, a point our guide to the best melatonin for dogs in the UK works through product by product.

"My dog ate 10 mg" — the real question isn't the melatonin

This is the scenario that sends owners searching at midnight, usually after a dog has helped itself to an imported bottle of gummies or a dropped tablet. The answer has two halves.

Step 1: the melatonin itself

Melatonin has a wide safety margin in dogs. The main documented effect of too much is drowsiness, sometimes with an upset stomach. A 10 mg dose is several times the chart for any dog under 45 kg, so a few groggy hours would not be surprising, but melatonin is rarely the ingredient that turns this into an emergency. Our article can I give my dog 10 mg of melatonin? covers the realistic limits, and melatonin side effects in dogs covers what to watch for at normal doses.

Step 2: check the label for xylitol — this is the actual risk

Xylitol, a sugar-free sweetener, is the reason human melatonin products can be dangerous to dogs. According to the Merck Veterinary Manual, xylitol above roughly 100 mg/kg has been associated with dangerously low blood sugar (hypoglycaemia), and above 500 mg/kg some dogs develop severe liver failure. Signs of hypoglycaemia can start within 30 minutes or be delayed by 12–18 hours; signs of liver injury may not appear for 24–48 hours; and activated charcoal does not usefully bind xylitol.⁹ In one case series of eight dogs with liver failure after eating xylitol, five died or were put to sleep.¹⁰

In a 2015 warning with the RSPCA, the UK's Veterinary Poisons Information Service reported that 97% of its xylitol enquiries over three years involved dogs, most often after chewing gum, with lozenges, baked goods and painkillers also to blame.¹¹ As a simple illustration, a 5 kg dog reaches the 100 mg/kg threshold at about 500 mg of xylitol — and the amount per gummy is rarely printed.

Xylitol hides under several names: birch sugar, birch sap, wood sugar, E967, xylit, xylite. It usually sits among the "other" or inactive ingredients, so its position on the list tells you nothing about how much is present.

What to do, in order

1. Find the actual pack and read the full ingredient list, including the inactive ingredients.
2. If xylitol or any of its other names appears, ring your vet straight away — or, out of hours, an out-of-hours vet service such as Vets Now or Animal PoisonLine on 01202 509000 (run by the Veterinary Poisons Information Service, open 24 hours; a fee of £35–£45 per call applies).¹² Do not wait for symptoms: the dangerous window can be delayed by hours.
3. If there is no xylitol, note how many milligrams of melatonin were swallowed and your dog's weight in kilograms, then call your vet for advice. Expect sleepiness.
4. Either way, keep the packaging. Whoever advises you will want the exact product, strength and number missing.

Timing: when to give it and what to expect

Give melatonin roughly 30 minutes before the moment you need it — bedtime, the car journey, the first rockets on Bonfire Night, the guests arriving on Christmas Eve. Giving it once your dog is already pacing and panting leaves it working uphill. Our guide to the best time to give a dog melatonin covers timing for each situation.

• From 30 minutes to 2 hours: some dogs settle noticeably; others show nothing on a first low dose. Both are normal.
• After about 2 weeks of situational or night-time use: enough repetitions to judge whether there is a consistent pattern, and a sensible point to review the dose with your vet.
• Coat conditions: hair regrowth is slow by nature, so dermatological use is judged over months, not weeks, and always with your vet.

Common dosing mistakes

• Splitting a human tablet to hit 1.5 mg. Fragments are not uniform, the label may already be well off, and UK slow-release tablets are designed not to be cut at all.
• Treating the chart as a prescription. It is a convention, not a trial result. Start low and confirm with your vet.
• Escalating the dose when nothing happens. Absorption in dogs is not proportional, so increases belong with your vet.
• Skipping the inactive ingredients. Xylitol lives there, and the list is not ordered by amount.
• Dosing more often than every 8 hours without veterinary direction.
• Stacking calming products. Melatonin alongside trazodone, gabapentin, benzodiazepines, acepromazine or other sedating medicines can add up. Tell your vet about every medicine and supplement your dog takes, including any prescribed for noise fear.
• Starting on the big night. Try the dose on a quiet evening first so you know how your dog responds before Bonfire Night or a long journey.

Who should not have melatonin without veterinary direction

• Pregnant, nursing or breeding dogs. In a 2025 controlled study, 16 intact male Pomeranians were randomly assigned to placebo or melatonin at 0.1, 0.3 or 0.5 mg/kg twice daily for 45 days; semen quality and testicular blood flow changed in a dose-dependent way and the testosterone-to-oestradiol ratio fell.¹³ Melatonin clearly acts on reproductive hormones, so breeding dogs should only have it on your vet's advice.
• Puppies. Safety data are limited; ask your vet first.
• Dogs with diabetes, liver disease or epilepsy, or any dog on regular medication, including sedatives and anticoagulants.
• Older dogs with new night-time restlessness. Pain, cognitive changes or other illness can look like "poor sleep" and need a vet check before any supplement.

Call your vet promptly if your dog is unusually hard to rouse, has persistent vomiting or diarrhoea, becomes agitated rather than calmer, or if anxiety or sleeplessness is severe or getting worse. Those can signal an underlying problem that no supplement addresses. If digestive signs are driving this decision, keep parasite testing in the conversation too: the dewormer coverage guide explains why a supplement label and confirmed parasite coverage are different things.

When the trigger is chronic, not one-off

This chart is built for event-based and sleep-related use: fireworks tonight, a ferry crossing tomorrow, a rough patch of senior sleeplessness. Dogs with daily, generalised anxiety usually need a broader plan, and UK owners will meet several other options: For an older dog whose nutrition plan also includes eye support, review eye supplements and what canine research supports before adding another antioxidant formula with overlapping ingredients. For the wider care plan as a dog ages, the senior-dog immune-support checklist helps you review nutrition, existing supplements and veterinary follow-up together.

• Vet-prescribed medicines (POM-V): Sileo, a gel applied to the gums that is authorised in the UK for acute anxiety and fear associated with noise, and Pexion (imepitoin) tablets, authorised for noise phobia and started two days before an expected event.¹⁴
• Over-the-counter calming products: Zylkene (milk-protein alpha-casozepine), YuMOVE Calming Care (Lintbells; lemon balm and L-theanine, no melatonin), Adaptil pheromone diffusers and Pet Remedy sprays, all sold by UK retailers such as the PDSA Pet Store and Zooplus UK. As a guide, Zooplus UK listed Zylkene 75 mg (30 capsules) at £27.09 when checked in October 2026.
• Behaviour support: desensitisation to recorded noises, a safe den, and a referral to a qualified behaviourist through your vet.

Many owners pair melatonin for the predictable nights with gentler everyday ingredients such as L-theanine and alpha-casozepine. Our ranking of the best calming supplements for dogs in the UK compares the main options by evidence.

Why the delivery form decides whether you can dose accurately

Two of the three problems above — uneven tablet fragments and sweeteners in gummies made for people — are format problems. A 1 mg or 1.5 mg dose cannot be produced reliably by breaking a human tablet, and an imported gummy may contain xylitol and far more melatonin than it says.

Our Melatonin for Dogs drops are a liquid standardised at 3 mg of melatonin per millilitre, so 0.33 mL, 0.5 mL, 1 mL and 2 mL read straight off the dropper. Every active is declared per millilitre with no proprietary blend — melatonin 3 mg, L-theanine 50 mg, alpha-casozepine 25 mg, water-soluble chamomile extract 25 mg, elemental magnesium 5 mg and vitamin B6 as P5P 0.5 mg — which is precisely what the JAMA and sleep-medicine label analyses show you cannot take for granted. The formula is xylitol-free with no artificial dyes, made in North America under GMP, and every batch comes with a certificate of analysis (COA). It holds a 4.6 out of 5 rating from 99 reviews on our UK store.

For UK owners it costs £25 a bottle (Buy 2 get 1 free for £50, or Buy 3 get 2 free for £75), with free delivery to the UK and duties and VAT prepaid, so there is no customs charge or Royal Mail fee to pay on the doorstep. Show the per-mL panel to your vet and agree the starting volume for your dog's weight.

Frequently asked questions

How much melatonin can I give my dog by weight?

The commonly cited amounts are about 1 mg for dogs under 4.5 kg, 1.5 mg for 4.5–11 kg, 3 mg for 11–45 kg and 3–6 mg over 45 kg, up to three times a day and at least 8 hours apart. These figures come from clinical convention rather than a dose-ranging trial, so start at the low end of your dog's band and confirm the amount with your vet.

Can I give my dog 10 mg of melatonin?

Ten milligrams is above the amount commonly cited for any weight band. Melatonin has a wide safety margin and the main effect of too much is drowsiness, sometimes with an upset stomach. The bigger worry with a human 10 mg tablet or gummy is xylitol: check the full ingredient list and, if xylitol or birch sugar appears, contact your vet or Animal PoisonLine (01202 509000) immediately.

Why doesn't melatonin seem to work on my small dog?

Canine research found oral bioavailability of only 16.9% at 1 mg/kg because the liver clears much of a low dose before it reaches the bloodstream. Absorption in dogs is not proportional, so do not increase the dose on your own — check the timing first, then discuss the dose with your vet.

How long before bedtime should I give melatonin?

About 30 minutes before your dog's usual bedtime, or before the stressful event. Giving it before your dog is already unsettled is far more useful than giving it afterwards.

How much of a 3 mg/mL liquid equals a 1.5 mg dose?

0.5 mL. At 3 mg per millilitre, 1 mg is 0.33 mL, 1.5 mg is 0.5 mL, 3 mg is 1 mL and 6 mg is 2 mL. Recalculate if your product uses a different strength.

Is melatonin licensed for dogs in the UK?

No. No melatonin product is authorised by the Veterinary Medicines Directorate for dogs, and for people the NHS lists melatonin as prescription-only. A UK vet can prescribe melatonin for a dog under the cascade and will set the dose. Dog calming supplements that contain melatonin are not authorised medicines, so check the declared amount per mL and tell your vet you are using one. For the anxiety-specific melatonin question, see melatonin and dog anxiety.

Can I use my own prescribed melatonin tablets for my dog?

No. A prescription is for the person it was written for, and the common UK 2 mg slow-release tablet must not be cut or crushed, so it cannot be turned into a 1 mg or 1.5 mg dog dose. Ask your vet instead; they can prescribe a suitable product for your dog or advise on a measurable dog formula.

References

1. NHS. About melatonin; How and when to take melatonin. nhs.uk
2. Veterinary Medicines Directorate. The cascade: prescribing unauthorised medicines. gov.uk
3. Chen M, Stone R. Lack of effect of oral melatonin on platelet parameters in normal healthy dogs. J Am Anim Hosp Assoc. 2019;55(5):226-230. PMID 31433224. PubMed
4. Shipstone M. Merck Veterinary Manual, canine alopecia and flank alopecia (melatonin), updated June 2026. merckvetmanual.com
5. Yeleswaram K, McLaughlin LG, Knipe JO, Schabdach D. Pharmacokinetics and oral bioavailability of exogenous melatonin in preclinical animal models and clinical implications. J Pineal Res. 1997;22(1):45-51. PMID 9062870. PubMed
6. Niggemann JR, Tichy A, Eberspächer-Schweda MC, Eberspächer-Schweda E. Preoperative calming effect of melatonin and its influence on propofol dose for anesthesia induction in healthy dogs. Vet Anaesth Analg. 2019;46(5):560-567. PMID 31351807. PubMed
7. Cohen PA, Avula B, Wang YH, et al. Quantity of melatonin and CBD in melatonin gummies sold in the US. JAMA. 2023;329(16):1401-1402. PMID 37097362. PMC
8. Erland LA, Saxena PK. Melatonin natural health products and supplements: presence of serotonin and significant variability of melatonin content. J Clin Sleep Med. 2017;13(2):275-281. PMID 27855744. PubMed
9. Merck Veterinary Manual. Xylitol toxicosis in dogs (reviewed September 2024). merckvetmanual.com
10. Dunayer EK, Gwaltney-Brant SM. Acute hepatic failure and coagulopathy associated with xylitol ingestion in eight dogs. J Am Vet Med Assoc. 2006;229(7):1113-1117. PMID 17014359. PubMed
11. VN Online. Pet owners reminded about dangers of xylitol (VPIS and RSPCA warning), 2015. vnonline.co.uk
12. Animal PoisonLine (Veterinary Poisons Information Service), 01202 509000. animalpoisonline.co.uk
13. Abdous A, Jokar M, Farhoodi M, Shirani D, Moayer F. Dose-response effects of oral melatonin on reproductive parameters in intact male Pomeranian dogs with Alopecia X: a controlled study. Vet Med Sci. 2025;11(3):e70410. PMID 40358664. PubMed
14. Veterinary Medicines Directorate, Product Information Database: Sileo 0.1 mg/ml oromucosal gel for dogs; Pexion tablets for dogs. vmd.defra.gov.uk

This article is for general information only and is not a substitute for advice from your vet. Melatonin is not authorised as a veterinary medicine for dogs in the UK; vets may prescribe it under the cascade. Supplements are not intended to diagnose, treat or prevent any disease. Talk to your vet before starting melatonin or any supplement, especially if your dog is pregnant, nursing, used for breeding, a puppy, diabetic, epileptic, on any medication or has a health condition. If you think your dog has swallowed something harmful, contact your vet or Animal PoisonLine (01202 509000) straight away.