Melatonin Side Effects: the Good and the Bad

You are right in checking out melatonin’s side effects. You want to try this popular natural sleep aid or have started on it for a while that you want to know if you are experiencing some melatonin side effects.

Melatonin is undoubtedly one of the most popular over the counter sleep aids. You would probably be familiar by now about its benefits especially in jet lag and getting your internal body clock back on track. However, the U.S. Food and Drug Administration does not strictly regulate herbs and supplements. Long-term studies on humans are also not available.

The good news is melatonin is generally regarded as safe in recommended doses for short-term use (three months or less) according to the National Institute of Health (NIH).  Looking at available studies and clinical use, melatonin’s overall side effects are not significantly more common than placebo, the control group that didn’t take melatonin. Commonly experienced melatonin side effects include fatigue, dizziness, headache, irritability, and sleepiness, although these effects may occur due to jet lag and not to melatonin itself.

In that context of its overall safety profile, you should still keep a watch out for out-of-the-norm melatonin side effects that have been reported and raised some concerns. These are:

1.    Blood clotting abnormalities (particularly in people taking warfarin)

2.    Seizures
Melatonin may lower seizure threshold and increase the risk of seizure, particularly in children with severe neurologic disorders. However, multiple other studies actually report reduced incidence of seizure with regular melatonin use. Hence, this remains an area of controversy.

3.    Disorientation with overdose
This is accompanied by confusion, sleepwalking, vivid dreams, and nightmares. Fortunately, these melatonin side effects often resolve after stopping melatonin.

4.    Mood changes including giddiness and dysphoria (sadness)

5.    Psychotic symptoms
Hallucinations and paranoia are possibly due to an overdose. People with underlying major depression or psychotic disorders taking melatonin should be monitored closely by a healthcare professional.

6.    Hormonal changes

This affects both men and women. For men, increased breast size (gynecomastia), decreased sperm count and decreased sperm motility have been reported. Fortunately, these are resolved after stopping melatonin.

For women, decreases or increases in levels of reproductive, thyroid and growth hormones have been reported. High levels of melatonin during pregnancy may increase the risk of developmental disorders. In animal studies, melatonin is detected in breast milk.

7.   Elevated blood sugar levels (hyperglycemia)
This melatonin side effect is mainly reported in patients with type 1 diabetes (insulin-dependent diabetes). Low doses of melatonin reduced glucose tolerance and insulin sensitivity in these cases.


Avoid Melatonin if:
1.    You are taking the blood-thinning medication like warfarin, aspirin or heparin.
2.    You have neurologic disorders and taking anti-epileptic drugs
3.    You are suffering from depression or other psychotic disorders
4.    You have diabetes especially Type 1 diabetes
5.    You are pregnant or are a nursing mother


Overall, don’t throw the baby out with the bath water. Always weigh the benefits versus the risks of any natural sleep aid. Find not just any doctor but one who is familiar with your health profile to help you weigh the benefits and side effects of melatonin. Remember that with all natural sleep aids, not just melatonin, always use them for the short term to solve your sleep problems.