Melatonin for Sleep: Dosage, Timing and Limits

What Melatonin Actually Does

Melatonin is a hormone produced by the pineal gland in response to darkness. Its primary biological function is signalling the timing of the sleep-wake cycle, it does not generate sleep itself, but communicates to the body's circadian system that night has arrived and sleep is appropriate.

Natural melatonin secretion begins 1-2 hours before habitual sleep onset (the dim-light melatonin onset, or DLMO), rises during the night, and suppresses in the morning in response to light exposure. The peak physiological melatonin concentration during a normal sleep night is approximately 100-200 picograms per millilitre, a very small quantity.

Light is the primary suppressor of melatonin. Blue-spectrum light (from screens, LED lighting, bright indoor environments) is particularly potent at suppressing melatonin secretion. This is why bright light exposure in the evening delays the melatonin signal and makes it harder to fall asleep at an earlier time.

This mechanism explains both what melatonin supplementation does and does not do:

• It shifts the timing of the sleep-wake cycle
• It does not increase total sleep time in people with normal circadian timing
• It does not reduce waking after sleep onset in most contexts
• It is not a sedative in the pharmacological sense, it does not work like benzodiazepines or antihistamines

What Melatonin Helps With

Jet Lag

Jet lag is a circadian disruption, the body's internal clock is misaligned with the local time zone after rapid transmeridional travel. Melatonin accelerates resynchronization of the circadian clock to the new time zone. The Cochrane Review on melatonin for jet lag (Herxheimer & Petrie, 2002, updated) concluded that melatonin is remarkably effective for preventing or reducing jet lag, particularly for flights crossing five or more time zones, and especially for eastward travel.

Evidence-based jet lag protocol:

• For eastward travel: take 0.5-5 mg at the target destination bedtime for 2-4 nights after arrival. This advances the circadian clock toward the new time zone
• For westward travel: melatonin may be less necessary as westward travel tends to cause less severe jet lag; if used, take at the local bedtime in the destination
• Combining melatonin with light exposure management (bright light in the morning at the destination, avoiding light in the evening) accelerates adaptation

Delayed Sleep Phase Disorder (DSPD)

DSPD is a circadian rhythm disorder characterized by a sleep phase that is significantly delayed relative to conventional schedules, natural sleep onset at 2-4 AM and natural wake time of 10 AM-noon. People with DSPD are not "night owls by choice"; their circadian clock is genuinely shifted later. Melatonin taken 4-6 hours before the current (delayed) sleep onset time, combined with morning bright light therapy, is a first-line treatment for DSPD. This is a case where melatonin's timing-shifting properties directly address the underlying problem.

Shift Work Circadian Disruption

Shift workers whose schedules change the sleep-wake timing can use melatonin to facilitate sleep at atypical times. Effectiveness is higher for night shift workers trying to sleep during the day than for variable shift workers whose schedules change irregularly.

Age-Related Melatonin Decline

Melatonin production declines with age. Older adults naturally produce less melatonin, which contributes to lighter, more fragmented sleep and earlier wake times in many older people. Low-dose melatonin (0.5-1 mg) in older adults may address a genuine deficit in this population, making supplementation more physiologically appropriate than in younger adults with normal melatonin production.

What Melatonin Does Not Help With

Chronic Insomnia (Most Cases)

Chronic insomnia, difficulty falling or staying asleep occurring at least three nights per week for three or more months, is primarily maintained by psychological and behavioural factors: hyperarousal, conditioned wakefulness, catastrophic thinking about sleep, and sleep-incompatible habits. These factors are not caused by low melatonin levels.

A 2013 meta-analysis (Ferracioli-Oda, Qawasmi, and Bloch, PLOS ONE) found that melatonin reduced sleep onset latency by an average of about 7 minutes compared to placebo, a statistically significant but clinically modest effect. For comparison, Cognitive Behavioural Therapy for Insomnia (CBT-I) reduces sleep onset latency by an average of 30-50 minutes and achieves remission in 70-80% of cases.

If you take melatonin for difficulty falling asleep and it helps substantially, it is worth considering whether your sleep difficulty is actually a circadian timing issue (DSPD or irregular schedule) rather than insomnia, in which case melatonin is addressing the actual problem. If melatonin provides only modest or no benefit for your sleep difficulty, the cause is likely not a melatonin deficiency.

Difficulty Staying Asleep

Melatonin has limited evidence for reducing night waking or improving sleep maintenance. Its action is primarily at sleep onset timing. People who fall asleep easily but wake at 3-4 AM and cannot return to sleep are unlikely to benefit from melatonin for that specific problem.

Stress-Related Poor Sleep

Acute stress activates the hypothalamic-pituitary-adrenal axis, elevating cortisol, which is in biological opposition to melatonin's sleep-promoting signal. In periods of high stress, the cortisol system effectively overrides melatonin timing. Melatonin supplementation during stress-related poor sleep addresses the wrong mechanism.

Dosage: Why Less Is More

The most important and most counterintuitive fact about melatonin dosing is that the commonly available commercial doses are far in excess of what is needed for effect.

Research by Lewy et al. and others has established that 0.5 mg (500 mcg) produces physiologically meaningful melatonin elevation sufficient for circadian timing effects. A dose of 0.5-1 mg is effective for jet lag, DSPD, and age-related melatonin decline.

Most commercial melatonin in Canada is sold in 2.5 mg, 5 mg, or 10 mg formulations, 5 to 20 times the evidence-based dose. A 5 mg dose raises blood melatonin to levels approximately 20 times higher than natural nighttime peaks. A 10 mg dose is supraphysiological to an extreme degree. Higher doses do not produce proportionally better sleep outcomes; they produce longer duration of elevated melatonin (sometimes extending into the morning, causing grogginess) and raise theoretical concerns about feedback effects on the pineal gland's natural secretion over time.

Practical dosage guidance:

• For jet lag: 0.5-1 mg taken at local target bedtime at the destination. If only 2.5 mg tablets are available, splitting is reasonable
• For delayed sleep phase / circadian timing: 0.5-1 mg taken 4-6 hours before current sleep onset (early in evening) to shift sleep earlier
• For general sleep support / age-related decline: 0.5-1 mg taken 30-60 minutes before target bedtime
• What to avoid: Starting at 10 mg as a routine dose; this is a common but poorly-supported practice

Timing Matters More Than Dose

When you take melatonin matters as much as how much you take, and the correct timing is not intuitive for most people.

Common misuse: taking melatonin when you are already in bed unable to sleep. At that point, the window for shifting the sleep-timing signal has passed. Melatonin taken when lying in bed awake at midnight will have minimal effect on falling asleep at that moment, it will shift the next night's sleep timing slightly later, which is the opposite of what most people want.

Correct timing by use case:

• To fall asleep earlier (advance the sleep phase): Take 0.5-1 mg approximately 5-6 hours before current sleep onset. If you naturally fall asleep at 1 AM and want to fall asleep at 11 PM, take melatonin around 7-8 PM. This feels counterintuitive but is mechanistically correct
• For jet lag (eastward): Take at the destination's local bedtime, even if that feels like afternoon or early evening by your home time zone
• For general sleep support: Take 30-60 minutes before your target bedtime. If you want to be asleep by 11 PM, take at 10-10:30 PM
• Not helpful: Taking melatonin when you are already unable to sleep and have been awake for some time

Melatonin in Canada

Health Canada regulates melatonin as a natural health product (NHP) rather than a prescription medication. This means:

• It is available over the counter without a prescription at pharmacies, health food stores, and general retailers
• The regulatory standard for safety and efficacy evidence is lower than for prescription drugs
• Product quality varies between manufacturers, look for products with NPN (Natural Product Number) registration, which indicates the product has met Health Canada's basic quality and safety review
• Health Canada has approved melatonin for jet lag, sleep restriction (shift work), and as a sleep aid for people 55 and older at doses of 0.5-10 mg

Most Canadian pharmacies carry multiple melatonin formulations. Immediate-release tablets are the standard form. Extended-release formulations are marketed for sleep maintenance (waking in the night) but have limited additional evidence over immediate-release for most users. Sublingual drops and liquid formulations may have faster onset than tablets.

Side Effects and Cautions

• Morning grogginess: The most common side effect, particularly with higher doses (5-10 mg) or extended-release formulations. Reflects elevated melatonin levels persisting into morning. Reducing the dose typically resolves this
• Vivid dreams: Reported by some users, particularly at higher doses
• Headache: Reported in a minority of users
• Drug interactions: Melatonin may interact with anticoagulants (blood thinners), immunosuppressants, diabetes medications, and medications that affect the liver's CYP1A2 enzyme. If you are on these medications, consult your physician before regular melatonin use
• Pregnancy and breastfeeding: Insufficient evidence on safety; avoid unless directed by a physician
• Children: Short-term melatonin use in children is generally considered safe for specific indications (jet lag, circadian issues related to neurodevelopmental conditions). Long-term nightly use in children without medical indication should involve physician guidance, as the developing hormonal system is potentially more sensitive to exogenous hormones than the adult system
• Autoimmune conditions: Melatonin has immunomodulatory properties; people with autoimmune conditions should consult their physician before regular use

When Melatonin Is the Wrong Tool

Melatonin is useful for a specific set of sleep problems. If your sleep difficulty is not in that category, investing in melatonin does not address the underlying cause:

• Chronic insomnia: CBT-I is the evidence-based first-line treatment. CBT-I addresses the psychological and behavioural maintenance factors that perpetuate insomnia. In Canada, CBT-I is available through psychologists, some GPs, and digital programs (Sleepio, Insomnia Coach). It is more effective than any sleep medication including prescription sedatives, with effects that persist after treatment ends
• Sleep apnea: Sleep apnea causes sleep fragmentation through airway obstruction. Melatonin does not address airway obstruction. If you have symptoms of sleep apnea (loud snoring, witnessed apneas, morning headaches, excessive daytime sleepiness despite adequate sleep time), a sleep study is the appropriate next step, not melatonin
• Restless leg syndrome: RLS causes discomfort that disrupts sleep. Melatonin does not address the dopaminergic and iron-related mechanisms underlying RLS
• Pain-related sleep disruption: Chronic pain disrupts sleep through a mechanism entirely separate from melatonin levels
• Sleep environment problems: A mattress causing discomfort, a bedroom that is too warm, or a partner with disruptive sleep patterns are physical causes of poor sleep that melatonin cannot address

Frequently Asked Questions

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Related Reading

• How to Fix Your Sleep Schedule Fast: Evidence-Based Reset Guide
• Sleep Syncing: How to Align Your Sleep to Your Natural Circadian Rhythm
• Melatonin for Sleep: Dosage, Timing & What the Research Says
• Melatonin for Sleep: A Canadian Guide to Dosage, Timing, and Safety
• How Long Does Melatonin Take to Work? (Timing Your Dosage) | Mattress Miracle