Melatonin Side Effects and Interactions
Melatonin is widely used and, for short periods at low doses, is generally described as well tolerated in healthy adults. The considerations worth knowing fall into three groups.
Commonly reported effects
Daytime drowsiness, headache, dizziness and nausea are the effects most often described. Next-day grogginess is more likely at higher doses and with extended-release products, and it matters practically if you drive or operate machinery in the morning.
Medication interactions
Melatonin interacts with several medication classes. If you take any regular prescription, ask a pharmacist before starting.
- Anticoagulants and antiplatelet medicines — potential effect on bleeding risk.
- Anticonvulsants — interaction reported; relevant for anyone with epilepsy.
- Immunosuppressants — melatonin may affect immune function.
- Diabetes medication — possible effects on blood glucose.
- Blood pressure medication — interaction reported.
- Sedatives, and alcohol — additive drowsiness.
- Fluvoxamine and some other medicines — can raise melatonin levels considerably.
Who should seek advice before using it
- People who are pregnant or breastfeeding
- People with autoimmune conditions
- People with epilepsy or a seizure disorder
- People with a bleeding disorder or taking anticoagulants
- Children and adolescents — only on medical advice
- Anyone whose work involves driving or machinery shortly after waking
Product quality
Published analyses of melatonin products on the US market have found label and content discrepancies, and in some cases the presence of other compounds. This is a category-level issue rather than a claim about any particular brand, and it argues for products from manufacturers stating third-party testing.
Sleep problems that persist
Ongoing difficulty sleeping has causes — some of them treatable, some of them worth identifying — and a supplement can postpone that conversation. If sleep is a persistent problem, a doctor is the better first stop.
See also how much is too much and our medical disclaimer.