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. 
  • Melatonin is metabolized by CYP 2C19, levels of melatonin can be altered by medication that inhibit or induce CYP 2C19 liver enzymes. Consult your pharmacist before using Melatonin.

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.

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

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