Melatonin for Insomnia: Dosage, Indications and Lab Tests

Endocrinology ·

Melatonin for Insomnia: Dosage, Indications and Lab Tests

Melatonin is the world's best-selling "sleep aid" — and one of the most misused. People take it for any reason, treating it as a "harmless supplement," and then wonder why sleep doesn't improve. In reality, melatonin is a hormone with clear indications, specific dosing, and a narrow list of cases where it actually works. Here's when melatonin for insomnia is justified, which doses are effective, and which lab tests it makes sense to do before reaching for the bottle.

What Melatonin Is and Why It's Taken

Melatonin is a pineal hormone synthesized at night when darkness sets in. Its main function is to signal the whole body "time to sleep" — it doesn't induce sleep mechanically; it shifts the circadian rhythm and eases sleep onset.

Melatonin supplements are a synthetic analog of the endogenous hormone, producing a brief blood concentration peak that mimics the nighttime release. They are useful in strictly defined situations:

  • Shifted circadian rhythm (delayed sleep phase syndrome)
  • Shift work and night shifts
  • Jet lag across several time zones
  • Age-related melatonin deficiency (in older adults nighttime synthesis drops 50–70%)
  • Poor "darkness coupling" in people exposed to screens late in the evening

The effect of melatonin is NOT sedative. It does not "knock out" like a hypnotic — it merely facilitates natural sleep onset. So in "classic" stress- or iron-deficiency-related insomnia, melatonin often disappoints.

For melatonin biochemistry and physiology in detail, see the article melatonin: what it is.

When Melatonin Actually Works

Controlled trials show melatonin's effectiveness in:

High effectiveness:

  • Delayed sleep phase syndrome (falling asleep after midnight) — sleep onset shortened by 30–60 minutes
  • Jet lag (especially eastbound) — adaptation 1–2 days faster
  • Shift work — better sleep after a night shift
  • Insomnia in older adults with age-related melatonin deficiency — improved sleep quality
  • Insomnia in blind patients (loss of light context for the pineal gland)

Moderate effectiveness:

  • Insomnia in children with ADHD or ASD (under pediatrician supervision)
  • Insomnia on β-blockers (which suppress melatonin synthesis)

Low or no effectiveness:

  • Insomnia in stress with hypercortisolism
  • Insomnia with low ferritin, hypothyroidism, or hyperthyroidism
  • Chronic psychophysiological insomnia
  • Insomnia from sleep apnea

When Melatonin Doesn't Help

If a person takes melatonin for 4–6 weeks at an adequate dose and sees no effect — another insomnia cause must be found. The most common "opaque" causes:

  • Low ferritin (< 50 ng/mL) — restless legs syndrome and sleep fragmentation
  • Subclinical hypothyroidism (TSH > 2.5)
  • High evening cortisol — melatonin and cortisol are antagonists; in hypercortisolism exogenous melatonin gets lost in the signal
  • Magnesium deficiency — impaired GABA receptor function
  • Sleep apnea — laboratory and instrumental workup is mandatory

Full insomnia workup is in insomnia: causes and tests.

Dosage: Low Doses vs High Doses

Paradoxically, in insomnia low melatonin doses (0.3–0.5 mg) are often more effective than high (5–10 mg). The reason: a low dose produces a physiological peak mimicking the natural release; a high dose causes a pharmacological "flood" that quickly desensitizes receptors.

Condition Recommended dose Timing
Circadian rhythm shift 0.3–0.5 mg 5–7 hours before desired sleep
Jet lag 0.5–3 mg 30 minutes before sleep at new local time
Age-related deficiency 0.5–1 mg 30 minutes before sleep
Shift work 1–3 mg Before daytime sleep after a night shift
Children (with clinician) 0.5–3 mg 30 minutes before sleep

Doses of 5–10 mg are usually excessive and confer no advantage. Long-term use of high doses suppresses endogenous melatonin synthesis — after stopping, sleep can be worse than before starting.

Which Tests to Take Before Starting

Before self-prescribed melatonin, it makes sense to check:

  • TSH + free T4 — exclude hypo- or hyperthyroidism
  • Ferritin — target > 50 ng/mL
  • Vitamin D (25-OH) — target 40–60 ng/mL
  • Morning and evening cortisol — assess circadian rhythm; if evening cortisol is elevated, melatonin may not work without lowering cortisol

For long-term use (more than 3 months) — assess nighttime melatonin (or a salivary series): low endogenous melatonin justifies replacement; normal levels suggest looking elsewhere.

All of these are conveniently drawn together as a sleep disorders panel.

Melatonin and Cortisol: An Antagonistic Pair

Melatonin and cortisol are biological opposites. In a healthy person their diurnal rhythms mirror each other: melatonin high at night, cortisol high in the morning. In chronic stress, evening cortisol stays elevated — blocking the "shift to night mode" even with exogenous melatonin.

So in cases of "the brain won't switch off" insomnia, the priority is lowering evening cortisol — not adding melatonin. For more, see how to lower cortisol and how to lower cortisol in women.

Once cortisol is normalized and melatonin remains low (visible on a nighttime sample), melatonin replacement is justified.

Side Effects and Contraindications

Melatonin in physiological doses (0.5–3 mg) is usually well tolerated. Possible side effects:

  • Morning sleepiness (especially with large doses or late timing)
  • Headache, dizziness
  • Nausea
  • Vivid dreams
  • Reduced libido (rare)
  • Mild immunosuppression with long-term high-dose use

Contraindications and caution:

  • Pregnancy and breastfeeding (limited data, not routinely prescribed)
  • Autoimmune disease (melatonin is an immunomodulator)
  • Epilepsy
  • Depression with suicidal ideation (melatonin may worsen)
  • Anticoagulants (potentiation)
  • Children — only under pediatric/sleep specialist supervision

Melatonin does not cause classic dependence, but long-term high-dose use can produce functional dependence by suppressing endogenous synthesis.

When to See a Sleep Specialist

If insomnia persists despite proper melatonin use — deeper assessment is needed:

  • Loud snoring with witnessed apneas (rule out sleep apnea)
  • Daytime sleepiness with adequate sleep duration
  • Parasomnias (sleepwalking, night terrors)
  • Chronic insomnia for more than 6 months

Laboratory diagnostics and sleep medicine are different tools. Melatonin belongs to the lab-endocrine approach; apnea is diagnosed only by polysomnography.

This article is for informational purposes only and does not replace professional medical advice. For long-term or regular melatonin use, clinical consultation is advisable.

Frequently Asked Questions

Short-term (up to 4–8 weeks) — usually safe, especially at low doses (0.3–0.5 mg). Long-term daily high-dose use suppresses endogenous synthesis — after discontinuation sleep can worsen. If melatonin is needed for more than 2–3 months, take a break and review the strategy with a clinician. Before long courses it is sensible to assess the insomnia cause via the sleep disorders panel — the cause may not be melatonin deficiency.

Paradoxically, lower doses (0.3–0.5 mg) often work better than higher ones. They create a physiological peak mimicking nighttime release. 5–10 mg doses are pharmacological, and receptors quickly desensitize to them. For most indications 0.5–1 mg 30 minutes before sleep is enough. Higher doses are justified for jet lag across multiple time zones and sometimes for shift work.

This is one of the most evidence-based indications. After a night shift, 1–3 mg before daytime sleep helps fall asleep faster and improves sleep quality. In parallel — room blackout, dark curtains, no phone screen light. Effectiveness has been demonstrated in clinical trials in healthcare workers and operators. For melatonin biochemistry, see melatonin: what it is.

Not recommended without clear necessity. Limited data exist in pregnancy; the evidence base is sparse. If insomnia in pregnancy is significant — priority goes to non-pharmacological strategies: sleep hygiene, magnesium, correction of iron and vitamin D deficiency, and psychotherapy. Melatonin during pregnancy is decided only with the obstetrician at the minimum effective dose. During lactation — case-by-case clinical evaluation.

For most people and most indications — 0.3–0.5 mg. High doses are justified only for jet lag or shift work. A small dose creates a physiological peak and does not suppress endogenous synthesis on long-term use; a large dose gives a sharper effect but more quickly creates functional dependence. If 0.5 mg doesn't help, that's often a sign the insomnia is not from melatonin deficiency — and a sleep disorders panel is appropriate.

Short courses (up to 4–8 weeks) — without serious concern. Long courses (more than 3 months) — only with confirmed deficiency (by nighttime testing) and clinical supervision. The best strategy is 4–6-week cycles with 2–4-week breaks. If melatonin is needed continuously for more than 6 months, that signals you are treating a consequence while the cause persists (often hypercortisolism or iron deficiency); see insomnia: causes and tests.

#Мелатонин#Кортизол#Ферритин#Панель при нарушениях сна

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