Melatonin Side Effects: What’s Normal, What’s Not, and Why Low Dose Is Safer
Melatonin side effects depend heavily on dose and timing. Melatonin is powerful—used wisely it can help with sleep onset, but excess can cause next-day grogginess and other issues.
What Melatonin Actually Does
Melatonin signals the brain that it’s night. It doesn’t sedate like a sleeping pill; it shifts circadian timing and supports natural sleep onset. That’s why dosing and timing (typically 30–45 minutes before bed) matter.
Common Melatonin Side Effects
- Morning grogginess/daytime sleepiness (more likely with 3–10 mg)
- Headache
- Nausea or digestive upset
- Dizziness or lightheadedness
- Vivid or unsettling dreams
Less commonly, some people report mood changes. Melatonin can interact with anticoagulants, antidepressants, and immune-active drugs—ask your clinician if you use these.
When to seek medical advice
- Severe or persistent dizziness, confusion (especially in older adults)
- Chest pain, fainting, or signs of an allergic reaction
- If you’re pregnant, breastfeeding, or take the interacting medicines above
Why Dosage Matters
- The brain produces about ~0.3 mg nightly.
- Research suggests 0.3–1 mg often improves sleep onset.
- Store tablets at 3–10 mg can be 10–30× physiologic and raise side-effect risk.
Higher doses don’t reliably improve sleep quality but do increase the chance of next-day drowsiness and REM disruption.
Why Low-Dose Is Often Best
In older adults, a trial (Wade et al., 2011) showed 0.3 mg restored near-physiologic levels while 5 mg increased morning sleepiness.
- Aligns with natural secretion
- Reduces grogginess risk
- Keeps REM sleep intact
- Gentler, more physiologic effect
Smarter Low-Dose Options
Supports sleep onset with fewer melatonin side effects than high-dose tablets.
Melatonin Side Effects — FAQ
How long do melatonin side effects last?
Most wear off within hours; next-day grogginess is more common with higher doses (3–10 mg).
Can melatonin cause vivid dreams?
Yes—especially at higher doses. Lowering the dose often helps.
Is melatonin safe to take every night?
For many healthy adults at low doses, yes. If you’re on interacting meds or pregnant/breastfeeding, talk to your clinician first.
