As a hormone, melatonin is released by the pineal gland and is involved in sleepwake cycles. As a supplement and medication, it is often used for the short-term treatment of disrupted sleep patterns such as from jet lag or shift work, and is typically taken orally.
The effect includes alterations in immune response and blood pressure, regulation of the cell cycle, and antioxidant protective properties. Melatonin is metabolized primarily by the liver through the use of cytochrome CYP1A2 [4]. The serum concentrations and bioavailability of melatonin are dependent on concomitant drug use.

Summary Melatonin overuse is becoming increasingly common, and experts warn that high or prolonged doses can cause hormonal changes, daytime drowsiness, headaches, and even rare neurological or liver issues. Melatonin has become one of the most widely used sleep aids in recent years.

Melatonin is a hormone that your body naturally makes. It comes in an OTC sleep aid. Its safe but could cause side effects if you take too much.

How long do melatonin side effects last? Melatonin side effectssuch as grogginess, dizziness, headache, or nauseausually resolve within a few hours as the supplement leaves your system.
Melatonin Side Effects and Can You Overdose?But we still dont know the implications for taking melatonin for the longer term, whether in adults or kids, and studies have revealed scarce evidence showing that it works for sleep difficulties. Lets take a deeper look What is melatonin?