Melatonin

Melatonin is the hormone your brain releases at night to tell your body it's time to sleep. Taken as a supplement, it does two different jobs depending on why you're using it. As a sleep aid it helps you fall asleep a bit faster, the effect is real but modest, think 7 to 12 minutes off your sleep onset on average, not a knockout. As a circadian tool it's much more powerful: taken at the right time it can shift your body clock, which is what makes it genuinely useful for jet lag, shift work, and a delayed sleep schedule.

The people who get the most out of it are travellers crossing time zones, anyone whose sleep timing has drifted late, older adults whose own melatonin production has dropped off, and people resetting a schedule. If you're a healthy sleeper who occasionally has a restless night, it will help a little. If your problem is a misaligned clock, it can help a lot if you get the timing right.

Deep-dive

Melatonin is produced by the pineal gland in response to darkness. Levels rise a couple of hours before your natural bedtime, peak in the middle of the night, and fall toward morning. It acts mainly on two receptors, MT1 and MT2, in the suprachiasmatic nucleus, the small region of the hypothalamus that runs your master clock. MT1 dampens the wake-promoting signal from that clock, MT2 is more involved in shifting its timing. This is the key thing to understand about melatonin: it is more of a clock signal than a sedative. It tells your brain "it is night," and the sleepiness follows from that, rather than from direct sedation the way alcohol or a benzodiazepine works.

The sleep effect is real but small. A 2013 meta-analysis of 19 randomised trials in roughly 1,700 people with primary sleep disorders found melatonin cut sleep onset latency by about 7 minutes, increased total sleep time by about 8 minutes, and modestly improved subjective sleep quality. A larger 2024 dose-response meta-analysis pulling from 26 trials found the effect on falling asleep and total sleep time grew with dose up to around 4 mg/day and then plateaued, with most of the benefit captured in the 3 to 5 mg range. A network meta-analysis of insomnia treatments found melatonin reliably shortened objectively measured sleep onset, but the effect on self-reported sleep quality and on staying asleep through the night was weak or absent. The honest summary: melatonin helps you fall asleep, it does little for sleep maintenance, and it is not in the same league as prescription hypnotics for raw sedative power. Its advantage is the side effect profile, not the potency.

The circadian effect is where it earns its place. Melatonin shifts the body clock according to a phase response curve, and the direction depends entirely on timing. Taken in the evening, a few hours before your natural melatonin onset, it advances the clock, moving you earlier. Taken in the morning, it delays the clock, moving you later. This is why timing matters more than dose for circadian use, and why a mistimed dose can actively push your clock the wrong way. For jet lag, the Cochrane review of 10 trials found melatonin taken close to target bedtime at the destination meaningfully reduced jet lag after crossing five or more time zones, with doses from 0.5 to 5 mg working similarly for the phase shift itself, the higher doses just add a bit of sedation on top. Eastward travel, where you have to advance your clock, responds better than westward.

Low dose versus high dose. Your pineal gland produces a tiny amount of melatonin, and doses around 0.3 to 0.5 mg are enough to raise blood levels into the normal night-time physiological range. Most supplements on the shelf are 3, 5, or 10 mg, which push levels far above anything your body would ever produce naturally. For the circadian phase-shifting effect, the low physiological dose is enough and arguably cleaner. The higher doses are more about the mild sedative add-on and tend to be the ones that cause next-day grogginess. More is not better here, it just shifts you from "clock signal" toward "blunt instrument," and the blunt instrument is not very sharp to begin with.

The antioxidant angle. This is the claim you have probably seen the most about, and it is real but routinely overstated. The mechanism is genuinely well-documented: melatonin is a direct free radical scavenger, it concentrates inside mitochondria where most free radicals are generated, and it upregulates the body's own antioxidant enzymes like superoxide dismutase and glutathione peroxidase. A 2014 review in the Journal of Pineal Research lays out the full cascade. The honest caveat that usually gets dropped: the human trials behind this were almost all done in people with conditions that involve high baseline oxidative stress, diabetes, kidney disease, dialysis patients, and there is very little evidence it does anything measurable for a healthy person with normal oxidative balance. The antioxidant activity is a genuine feature and a plausible part of why melatonin looks protective in aging research, but it is not a reason on its own for a healthy person to take it daily.

Older adults. This is one of the clearer use cases. Endogenous melatonin production declines with age, and the age-related drop in night-time melatonin is part of why sleep gets lighter and more fragmented in later life. Prolonged-release melatonin is actually approved in the UK, the EU, and Australia for short-term insomnia in adults over 55, on the logic that you are topping up something the body is no longer making enough of. Older adults also clear melatonin more slowly, so they should start low, both to avoid daytime carryover and because the dose needed is genuinely smaller.

Women. The core mechanism, the receptors, the clock, the phase response curve, is the same in women and men, and the sleep and jet lag trials have included women throughout without showing a need for a different approach. There are a few female-specific threads worth knowing. Endogenous melatonin interacts with the reproductive axis and fluctuates across the menstrual cycle, but this does not translate into a practical need to dose differently by cycle phase. The more studied area is menopause. Melatonin production declines through the menopausal transition alongside the rise in sleep complaints, and a 2021 systematic review of melatonin in menopausal women found modest improvements in sleep quality, with effects on broader menopausal symptoms and mood inconsistent. Separately, melatonin has been studied for postmenopausal bone health: a one-year randomised trial in postmenopausal women with osteopenia tested 1 to 3 mg nightly and found it well tolerated with signals toward improved bone markers, though most of the positive bone-density results, like the MOTS trial, used melatonin combined with vitamin D, vitamin K2, and strontium, so melatonin's independent contribution to bone is still unclear. The practical takeaway for women: use it for the same reasons men do, sleep onset and circadian alignment, and treat the menopause sleep angle as a reasonable secondary use with real but modest evidence behind it. Pregnancy and breastfeeding are a different matter, safety data is thin, so it is generally avoided there.

What it does not do. Melatonin is not a treatment for chronic insomnia driven by anxiety, rumination, or poor sleep habits, the kind of insomnia where you are tired but wired. For that, the clock is not the broken part, and melatonin does not address the actual problem. It also does not deepen sleep architecture in any dramatic way, does not reliably keep you asleep, and builds no meaningful physical dependence, but it also does not fix an underlying sleep disorder. If your sleep problem is behavioural or stress-driven, L-Theanine, Glycine, Magnesium, or Apigenin target a different part of the picture, and behavioural approaches like consistent wake times and morning light do more than any supplement.

Product quality is a genuine issue. Because melatonin is sold as a supplement rather than a regulated drug in most places, what is on the label is often not what is in the bottle. An analysis of 31 melatonin products published in the Journal of Clinical Sleep Medicine found actual melatonin content ranged from 83% below to 478% above the label claim, with lot-to-lot variation within a single product as high as 465%. Some products also contained serotonin as an unlabelled contaminant. Chewables and gummies were among the worst offenders. This matters: if you are trying to take a clean low physiological dose and the product actually contains five times the label, you have lost the main advantage of dosing low. Buying products that carry independent verification, like a USP Verified mark, is the practical workaround.

Dosage:

For sleep onset: 0.5 to 5 mg, taken 30 to 60 minutes before bed. Start at the low end. Most people do not need more than 1 to 3 mg, and higher doses mostly add next-day grogginess rather than better sleep

For jet lag: 0.5 to 3 mg taken close to your target bedtime at the destination, starting the night you arrive and continuing for 2 to 4 nights until adjusted. Most effective crossing five or more time zones, and more useful for eastward travel than westward

For a delayed sleep schedule (you naturally fall asleep very late): a low dose, 0.5 to 1 mg, taken several hours before your current sleep onset, not at bedtime. Timing is the active ingredient here, taking it too late does little or pushes the wrong way. This use is worth getting right with some care, since the timing is counterintuitive

Older adults (over 55 to 60): start at 0.5 to 2 mg. Endogenous production is lower so the supplement is more relevant, but melatonin is also cleared more slowly, so the effective dose is smaller and daytime carryover is more likely. Prolonged-release forms are specifically designed for this group

Timing is the lever, not dose: for plain sleep onset, dose works fine. For anything circadian (jet lag, shifting a late schedule), when you take it determines whether it helps or hurts. Evening doses move you earlier, morning doses move you later

Forms: plain immediate-release tablets are fine for sleep onset and jet lag. Prolonged-release is the better fit for older adults or anyone whose issue is staying asleep rather than falling asleep. Avoid gummies and chewables if you can, they show the worst label accuracy. Look for an independent verification mark like USP Verified

Run it appropriately: for jet lag it is a few nights and done. For ongoing sleep-onset or schedule use, it is reasonable to use nightly for weeks, but it works best as a tool to reset or bridge rather than a permanent crutch, the underlying sleep timing and habits are what hold the result

Here's what you can expect:

Melatonin is subtle, not sedating. Within 30 to 60 minutes of a sleep-onset dose you may notice a mild drowsiness and a feeling that sleep is more available, but it does not pull you under the way a sleeping pill does. If you are expecting to be knocked out, you will be disappointed, and that disappointment is the single most common reason people conclude it "does not work." What it actually does is shave some time off how long you lie awake, and over a week or two of consistent use, modestly improve how rested you feel.

For jet lag and circadian use the experience is different and more impressive. You will not feel a dramatic acute effect on night one, but over the following days your sleep timing, appetite, and alertness re-anchor to the new schedule noticeably faster than they would on their own. Take one hour before your intended bedtime.

The most common unwanted effect is next-morning grogginess, more likely on higher doses (5 to 10 mg) and in people who metabolise it slowly. If that happens, the fix is a lower dose and an earlier dosing time, not stopping altogether. Vivid or unusually intense dreams are also commonly reported.

Side effects & risks:

Next-day grogginess and drowsiness is the most common issue, especially at 5 to 10 mg doses and in older adults who clear it slowly. Dose-dependent, resolves by lowering the dose and taking it earlier

Vivid dreams are frequently reported and harmless, though some people find them unpleasant

Wrong-direction circadian shift: taken at the wrong time of day, melatonin can push your body clock the wrong way and make sleep timing worse, not better. This is the most underappreciated risk and the reason timing matters for any circadian use

Headache, dizziness, nausea occur in a minority of people, usually mild and transient

Daytime sleepiness and impaired alertness if dosed too late or too high, which matters for driving and operating machinery the next morning

Interactions: melatonin is metabolised by the liver enzyme CYP1A2. Drugs that block this enzyme, notably fluvoxamine, can dramatically raise melatonin levels and increase grogginess. Caution combining with other sedatives, sleep medications, or alcohol, the effects stack. Melatonin may also have mild effects on blood pressure and blood glucose, worth knowing if you are on medication for either

Autoimmune conditions: melatonin has immune-modulating activity and the interaction with autoimmune disease is not well characterised, so caution is reasonable there

Pregnancy and breastfeeding: generally avoided, not because of documented harm but because safety data is thin

Children: melatonin is used in paediatric sleep medicine but should be a clinician-guided decision, not a casual one, and the product-quality problem is most acute in the chewables and gummies marketed for kids

Dependence: melatonin does not produce the physical dependence or rebound insomnia associated with prescription hypnotics. The main risk is psychological reliance and using it to paper over a fixable sleep-habit or stress problem

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Blood markers

For most people using melatonin occasionally for sleep or jet lag, no bloodwork is needed. It is one of the lower-risk compounds covered here and does not require routine monitoring.

Blood pressure and fasting glucose, baseline, are worth a reference point if you are using melatonin nightly and long-term, since it can mildly affect both, and more so if you are already on medication for blood pressure or diabetes.

HbA1c, baseline and then periodically, only if you have insulin resistance or diabetes and plan to use melatonin regularly, as the glucose-handling signal is more relevant in that group.

The people who actually need to think about testing are long-term nightly users, anyone on CYP1A2-affecting medication like fluvoxamine, and people with diabetes or blood pressure conditions. Short-term users for jet lag or the occasional bad night do not need baseline labs.

Sold as a dietary supplement in most countries, available by prescription only in some (including the UK and EU, where prolonged-release melatonin is approved for adults over 55).