Is Melatonin Safe? Dosage, Side Effects and What the Evidence Says

Melatonin is one of the most popular sleep supplements. It’s a hormone your brain naturally makes to signal bedtime, and taken as a supplement it’s used by many people to help with sleep. But how safe is it, what dose works, and what are the side effects?

This is general information, not medical advice - always check with a GP or pharmacist, especially if you take other medicines.

What melatonin is

Melatonin is a hormone the brain produces in response to darkness, helping regulate the body-clock (circadian rhythm). Melatonin levels naturally rise in the evening and fall in the morning. As a supplement, it’s taken to help ease sleep - particularly common for jet lag and shift work in some places.

Typical dosage

• Common adult doses range from about 0.5 mg to 5 mg, taken roughly 30-60 minutes before bedtime.
• Lower doses (around 0.5-1 mg) are often used, because more isn’t always better and higher doses can cause next-day drowsiness.
• The right dose varies by person; it’s sensible to start low.

Is it safe?

For most adults, short-term use is generally considered mild and well-tolerated. However:

• It’s not regulated like a medicine in many places (it’s a supplement), so product strength and quality vary.
• Long-term safety isn’t fully established - it’s best treated as a short-term aid, not a daily habit.
• Interactions matter: it can interact with blood-thinners, diabetes medication, immunosuppressants and some others - tell a pharmacist.

Source: NHS medicines information on melatonin; NIH Office of Dietary Supplements.

Possible side effects

Commonly reported effects with higher doses:

• Drowsiness or grogginess the next day
• Headache or dizziness
• Vivid dreams
• Occasionally mild stomach upset

Unlike many sleeping pills, melatonin is not thought to be habit-forming in the same way, but it still shouldn’t be relied on nightly without advice.

When to see a GP

If you’re regularly relying on melatonin, or your sleep isn’t improving after a few weeks, it’s worth seeing a GP. Long-term sleep problems are usually better addressed with sleep-hygiene habits and, where appropriate, structured treatment - not a supplement to mask the issue. (See our Sleep Hygiene guide.)

The one-line summary

Melatonin is a naturally-occurring hormone that can help some adults with sleep, in low doses (about 0.5-5 mg) taken shortly before bed. It’s generally mild for short-term use, but treat it as a short-term aid, watch for next-day grogginess, check interactions with a pharmacist, and see a GP if sleep doesn’t improve.

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Sources

• NHS - Melatonin: a medicine for insomnia and jet lag: https://www.nhs.uk/medicines/melatonin/
• US National Institutes of Health, NHLBI - Healthy Sleep Habits: https://www.nhlbi.nih.gov/health/sleep-deprivation/healthy-sleep-habits

This article is for general information and is not medical advice. Always consult a qualified healthcare professional before starting a supplement.