Melatonin Print Page

Common Names: Melatonin
Scientific NamesN-acetyl-5-methoxytryptamine

Bottom Line

Effectiveness: There is mixed evidence regarding the possible benefit of melatonin to improve sleep.  Some evidence shows melatonin has a trend towards benefit for improving sleep in patients with insomnia.

Safety: Melatonin seems to be safe for up to three months.

What is Melatonin?

  • Melatonin is a hormone made in the brain. Its production is affected by light, with more melatonin being produced when it is dark and less when it is light out.
  • The amount of melatonin in the blood is highest at night time.

What it is it used for in people with rheumatic conditions?

  • Melatonin has been used to improve sleep in patients with a variety of medical conditions. It is possible that melatonin may be able to help improve sleep in patients that have rheumatic conditions.

How is it thought to work?

  • Melatonin may help with sleep and jet lag by playing a role in regulating the body’s circadian rhythm (biological clock) and affecting sleep patterns. 

Does it Work? What the Science Says:

  • There have been many studies on melatonin for sleep with varying results. A meta-analysis of 14 medium quality studies (Jadad score 4) measuring sleep onset and efficacy in primary sleep disorders determined melatonin improved sleep but did not reach statistical significance, except in a subgroup of patients with delayed sleep phase syndrome.
  • A meta-analysis determined there is no evidence that melatonin is effective in treating secondary sleep disorders or disorders accompanying sleep restriction:
    • 6 medium quality RCTs (Jadad score 4) looked at sleep onset latency in patients with secondary sleep disorders: melatonin was not statistically different than placebo.
    • 9 medium quality RCTs (Jadad score 4) looked at sleep onset latency in people with sleep disorders accompanying sleep restriction (such as jet lag and shiftwork disorder): melatonin was not statistically different than placebo
    • 17 RCTs demonstrated that melatonin is safe (no adverse effects) when utilized for 3 months or less

What are possible side effects and what can I do about them?

  • Melatonin orally is generally well-tolerated. The most common side effect is daytime drowsiness (20%).
  • Some other less common but also noted side effects are headache, dizziness, mild tremor, mild anxiety, irritability, reduced alertness, confusion, nausea, vomiting and low blood pressure.


With drugs:

  • Theoretically, melatonin might increase the risk of bleeding in patients on anticoagulant/antiplatelet medications. The mechanism of this possible interaction is unknown but melatonin was shown to decrease plasma factors that make the blood clot.
  • Common antiplatelet and anticoagulant drugs may include: warfarin (Coumadin), ASA (Aspirin), clopidogrel (Plavix), ticagrelor (Brilinta), prasugrel (Effient), enoxaparin (Lovenox), dalteparin (Fragmin), dabigatran (Pradaxa), rivaroxaban (Xarelto), apixaban (Eliquis) and others.
  • Higher doses of melatonin (20mg) may boost immune function. There is no information available about low dose melatonin used for treatment of insomnia.
  • Fluvoxamine can increase melatonin levels by increasing absorption of melatonin and possibly reducing the removal of melatonin from the body. Monitor for drowsiness if using this combination.
  • Melatonin can cause daytime drowsiness and sedation and should be used with caution with other medications that also have these effects, such as benzodiazepines, alcohol and more.

With Other Diseases:

  • Theoretically, melatonin may worsen bleeding in patients with bleeding disorders, use with caution.
  • Melatonin can increase blood pressure in patients on blood pressure lowering medications, monitor blood pressure more carefully.
  • Melatonin may worsen seizures in certain patients (children with multiple neurological disorders), use with caution. 

With Other Natural Health Products:

  • The risk of bleeding may be increased if combined with other natural health products that also affect blood clotting.
  • Such as: garlic, ginkgo, ginger, certain types of ginseng, red clover, and others.

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For more information about Melatonin, consult your physician and pharmacist.