Magnesium vs Melatonin for Sleep
Two of the most popular sleep supplements, compared head-to-head using data from published meta-analyses.
Melatonin has stronger evidence for reducing the time it takes to fall asleep (19 RCTs, Grade A). Magnesium has promising data for overall sleep quality scores (9 RCTs, Grade B), but its prediction interval crosses zero.
They work through different mechanisms. Melatonin signals your body clock that it’s time to sleep. Magnesium relaxes muscles and activates the parasympathetic nervous system. Some people stack both, though no meta-analysis has tested the combination directly.
If your main problem is falling asleep, melatonin has the stronger evidence. If your sleep quality is poor and you suspect a magnesium deficiency (common in Western diets), magnesium is worth trying. Ask your doctor which makes more sense for your situation.
Magnesium
? MaybeStrong evidence for small blood pressure reductions. Modest evidence for sleep. Suggestive for anxiety. Doesn't prevent muscle cramps in most people.
Melatonin
✓ WorksStrong evidence for faster sleep onset and jet lag prevention. Modest evidence for sleep quality. Low doses (0.5-3mg) work as well or better than high doses.
Head-to-Head: sleep
Improves sleep quality
9 studies with over 7,500 people found magnesium modestly improves sleep quality scores. The effect is real but not huge. It helps more if you're …
Reduces time to fall asleep
19 studies with about 1,700 people found melatonin helps you fall asleep 7-10 minutes faster. That's not a huge effect, but it's real and consistent. …
Improves overall sleep quality
23 studies found melatonin improves sleep quality scores by about 1.24 points on the PSQI scale. That's a modest improvement. It works best for people …
Dosage Comparison
| Magnesium | Melatonin | |
|---|---|---|
| Dose Range in Studies | 200-400mg elemental | 0.5-3mg |
| Most-Studied Dose | 300-400mg elemental | 0.5-1mg for sleep onset, 3-5mg for jet lag |
| Best Form | Glycinate, citrate, or threonate (avoid oxide for absorption) | Immediate-release tablet or sublingual |
| Timing | Evening with food, especially for sleep | 30-60 minutes before bed for sleep, 3 hours before target bedtime for jet lag |
| Time to Effect | 1-4 weeks for sleep and anxiety. 4-8 weeks for blood pressure. | 30-60 minutes |
Safety
Magnesium Side Effects
- Loose stools or diarrhea (especially with oxide and citrate)
- Nausea at high doses
- Low blood pressure in sensitive individuals
Melatonin Side Effects
- Morning grogginess at high doses
- Vivid dreams or nightmares
- Headache (uncommon)
- Mild dizziness
- Nausea at very high doses