Patients ask me about sleep supplements constantly. “My naturopath recommended magnesium.” “I saw an ad for this ashwagandha blend.” “Melatonin didn’t work — should I try valerian?”

I understand the appeal. Supplements feel safer than prescription medications, they’re available without a script, and the marketing is convincing. But the evidence varies enormously, and I think people deserve an honest assessment rather than the “it’s natural so it must be fine” approach.

Here’s my ranking, based on clinical research quality. I’m focusing on supplements for general insomnia and sleep quality in adults, not specific conditions like jet lag or shift work.

Tier 1: Reasonable Evidence

Melatonin

Melatonin is the most-studied sleep supplement, and the evidence is… decent, but narrower than most people think. A meta-analysis in PLoS One found that melatonin reduced sleep onset latency by about 7 minutes and increased total sleep time by about 8 minutes compared to placebo.

That’s real but modest. Where melatonin genuinely shines is circadian rhythm disorders — delayed sleep-wake phase disorder, jet lag, and shift work adjustment. If your problem is falling asleep at the wrong time rather than not sleeping at all, melatonin is a reasonable option.

Dosing matters. Most over-the-counter products contain 3-10mg, which is far more than the 0.5-1mg that research suggests is optimal for sleep onset. Higher doses can actually cause morning grogginess and may reduce your body’s own melatonin production over time. Start low.

Magnesium

Magnesium has a plausible mechanism — it’s involved in GABA regulation, which is the brain’s primary inhibitory neurotransmitter. Several small studies have shown improvements in sleep quality, particularly in older adults who tend to have lower magnesium levels.

A 2012 study in the Journal of Research in Medical Sciences found that 500mg of magnesium supplementation improved subjective sleep quality, sleep time, and sleep efficiency in elderly participants with insomnia.

The evidence isn’t overwhelming, but magnesium is generally safe at recommended doses, has other health benefits, and is unlikely to cause harm. I’m comfortable recommending it as part of a broader sleep hygiene strategy. Magnesium glycinate or citrate are better absorbed than magnesium oxide.

Tier 2: Some Evidence, but Weaker

Glycine

This amino acid has interesting preliminary data. A small Japanese study found that 3g of glycine before bed improved subjective sleep quality and reduced daytime sleepiness. The proposed mechanism involves lowering core body temperature, which promotes sleep initiation.

I find the glycine research genuinely intriguing, but the studies are small and most come from a single research group. I’d like to see larger, independent replications before making strong recommendations. That said, glycine is safe and cheap, so trying it is low-risk.

L-Theanine

Found naturally in tea, L-theanine promotes relaxation without sedation. A few small studies suggest it may improve sleep quality, particularly in people with anxiety-related insomnia. It seems to work by increasing alpha brain wave activity, which is associated with a calm, alert state.

The evidence is modest but the safety profile is excellent. It won’t knock you out, but it may help quiet a racing mind at bedtime. Typical doses in studies are 200-400mg.

Tier 3: Weak or Inconsistent Evidence

Valerian Root

Valerian is one of the most popular herbal sleep aids, and I wish I could be more enthusiastic about it. The research is genuinely inconsistent. Some studies show modest benefits, others show nothing. A Cochrane review concluded that the evidence for valerian in insomnia is inconclusive.

Part of the problem is standardisation — different products contain different concentrations of active compounds, and it’s unclear which components are responsible for any sleep-promoting effects.

Ashwagandha

There’s growing interest in ashwagandha for sleep, and a few recent trials have shown modest improvements. However, most studies used combination products or assessed ashwagandha alongside other lifestyle interventions, making it hard to isolate the supplement’s effect.

I’m watching this space but not recommending it as a primary sleep intervention yet.

Tier 4: Insufficient Evidence or Concern

CBD

I know this is popular, and patients frequently tell me it helps them sleep. The clinical evidence is surprisingly thin. Most studies have been small, short-term, or focused on CBD’s effects on anxiety (which could secondarily improve sleep). There are also concerns about product quality — independent testing has found significant variability in actual CBD content versus label claims.

Tryptophan / 5-HTP

The logic (tryptophan converts to serotonin, which converts to melatonin) is sound, but the clinical evidence for sleep improvement is limited. There are also safety concerns about serotonin syndrome risk if combined with antidepressants.

My Bottom Line

If you want to try a supplement for sleep, melatonin (low dose, 0.5-1mg, taken 1-2 hours before desired sleep time) and magnesium glycinate (300-400mg) are the most evidence-supported options. Glycine and L-theanine are reasonable additions.

But here’s what I really want you to hear: no supplement substitutes for treating the underlying cause of poor sleep. If you have obstructive sleep apnea, no amount of magnesium will fix it. If you have chronic insomnia, cognitive behavioural therapy for insomnia (CBT-I) is vastly more effective than any supplement.

Supplements can be a useful piece of the puzzle. They’re rarely the whole answer.