Melatonin vs Magnesium for Sleep: Small Effects, Different Jobs

A meta-analysis of 19 placebo-controlled trials with 1,683 people found melatonin shortened time to fall asleep by 7.06 minutes, increased total sleep by 8.25 minutes and modestly improved sleep quality¹. The effects did not fade with continued use¹.

A 2024 dose-response analysis of 26 trials found benefits rose with dose up to about 4 mg a day, and were larger in people with insomnia and when melatonin was taken about 3 hours before the desired bedtime rather than the common 30 minutes². See how much melatonin to take and when for the details.

Melatonin does best when the problem is timing. In 116 people with delayed sleep-wake phase disorder and a late melatonin rhythm, all on a scheduled bedtime, 0.5 mg taken 1 hour before a set bedtime moved sleep onset 34 minutes earlier than placebo⁴. For chronic insomnia, the American Academy of Sleep Medicine issued a weak recommendation against using melatonin⁸.

Short-term melatonin use appears safe for most people, but data on long-term use are lacking⁶. Reported side effects were mild, such as headache, dizziness, nausea and sleepiness, and melatonin may stay active longer in older people and cause daytime drowsiness⁶. People with epilepsy or taking blood thinners should use it only under medical supervision⁶.

Label accuracy is a real issue. In an analysis of 31 melatonin supplements, content ranged from 83% below to 478% above the label, and 26% contained serotonin⁵.

High doses of magnesium from supplements can cause diarrhoea, nausea and cramping, and the risk of magnesium toxicity rises with poor kidney function⁷. Magnesium can bind some antibiotics, which should be taken at least 2 hours before or 4 to 6 hours after it, and can reduce absorption of oral bisphosphonates⁷.