Quick answer

Ask your pharmacist or doctor before combining. NCCIH says people who take blood thinner medicines need to be under medical supervision when using melatonin supplements. A Cochrane review noted case reports suggesting that people taking warfarin may come to harm from melatonin, and called for the possible interaction to be studied.^1,2

Key facts

NCCIH lists blood thinners and epilepsy as situations where people need medical supervision while using melatonin supplements.¹
A 2002 Cochrane review reported case reports suggesting that people taking warfarin may come to harm from melatonin, and said a possible interaction needs investigation.²
Neither NCCIH nor the Cochrane review explains how melatonin might interact with a blood thinner.^1,2
In a 2023 study, 22 of 25 melatonin gummy products were inaccurately labeled: one had no detectable melatonin and the rest held 74% to 347% of the labeled amount.³
The warfarin label tells prescribers to check INR more often when other drugs, including botanicals, are started or stopped. It does not name melatonin.⁴

Ask your pharmacist or doctor first

NCCIH says people taking blood thinner medicines need to be under medical supervision when taking melatonin. A Cochrane review noted case reports suggesting that people taking warfarin may come to harm from melatonin, and called for the possible interaction to be studied.^1,2

Reported in studies

Does melatonin interact with blood thinners?

MedlinePlus describes blood thinners as medicines that prevent blood clots from forming. The two main kinds are anticoagulants, such as warfarin and heparin, and antiplatelet medicines, such as aspirin and clopidogrel. It says blood thinners may interact with certain foods, medicines, vitamins and alcohol, and that your provider needs to know all the medicines and supplements you use.⁵

NCCIH's page on melatonin says people with epilepsy and those taking blood thinner medications need to be under medical supervision when taking melatonin supplements. It does not say why.¹

A 2002 Cochrane review of melatonin for jet lag found case reports suggesting that people taking warfarin may come to harm from melatonin. Its authors wrote that a possible interaction with warfarin needs investigation.²

How strong is the evidence on melatonin and blood thinners?

It is thin. The sources checked are a precaution from NCCIH and a note about case reports in a 2002 review. They include no trial of melatonin in people who take blood thinners, and none says melatonin thins the blood on its own. This pair is marked as coming from studies because it rests on reports like these, not on a warning printed on a blood thinner's label.^1,2

What does the warfarin label say about supplements?

The warfarin label says drugs, dietary changes and other factors affect INR, the blood test used to adjust the dose, and tells prescribers to monitor INR more often when starting or stopping other drugs, including botanicals. Melatonin is a hormone, not a botanical, and neither the label nor MedlinePlus's warfarin page names it, so this shows how the label treats outside products, not a finding about melatonin.^1,4,6

MedlinePlus asks people taking warfarin to tell their doctor and pharmacist about all vitamins, nutritional supplements and herbal or botanical products. The sources checked do not discuss melatonin with other blood thinners such as apixaban, rivaroxaban, aspirin or clopidogrel, apart from NCCIH's general statement about blood thinners. That is not a finding either way.^1,6

Do melatonin tablets and gummies make a difference?

The sources give no separate rule for tablets, gummies or liquids. NCCIH does warn that some melatonin supplements may not contain what is listed on the label.¹

In a 2017 study of 31 melatonin supplements, the amount in most products did not match the label, and 26 percent of them contained serotonin.^1,7

In a 2023 study, 22 of 25 melatonin gummy products were inaccurately labeled. One had no detectable melatonin, and the rest held 74 to 347 percent of the amount on the label.^1,3

For a person told to be supervised, that means the amount in a tablet or gummy may not be what the label says. That is worth telling your pharmacist.

What to ask your pharmacist about melatonin and your blood thinner

Which blood thinner do I take, and who monitors it with blood tests?
Should my prescriber know before I start, change or stop melatonin?
Is my melatonin a tablet, gummy or liquid, and what does its label say?
Do I take other supplements that may matter for my blood thinner?

Questions people ask

Can you take melatonin with blood thinners?

NCCIH says people on blood thinners need medical supervision when taking melatonin. Talk to your pharmacist or doctor before starting, so someone can watch for changes.¹

Does melatonin thin your blood?

The sources checked do not say that it does. They flag the combination with blood thinners, especially warfarin, for medical supervision and further study.^1,2

How does melatonin interact with blood thinners?

The sources do not explain how. NCCIH gives a precaution, and a Cochrane review mentions case reports about warfarin and asks for study.^1,2

Are melatonin gummies different from tablets when you take blood thinners?

The sources give no separate rule for gummies. A 2023 study found 22 of 25 gummy products inaccurately labeled, so the amount in a gummy may differ from the label.^1,3

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Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.