Melatonin is a hormone in your body that plays a role in sleep. The production and release of melatonin in the brain is connected to time of day, increasing when it's dark and decreasing when it's light. Melatonin production declines with age.

Melatonin is also available as a supplement, typically as an oral tablet or capsule. Most melatonin supplements are made in a lab.

People commonly use melatonin for sleep disorders, such as insomnia and jet lag.

Research on melatonin use for specific conditions shows:

• Circadian rhythm sleep disorders in the blind. Melatonin can help improve these disorders in adults and children.
• Delayed sleep phase (delayed sleep-wake phase sleep disorder). In this disorder, your sleep pattern is delayed two hours or more from a conventional sleep pattern, causing you to go to sleep later and wake up later. Research shows that melatonin reduces the length of time needed to fall asleep and advances the start of sleep in adults and children with this condition. Talk to your child's doctor before giving melatonin to a child.
• Insomnia. Research suggests that melatonin might slightly reduce the time it takes to fall asleep, but its effects on sleep quality and total sleep time aren't clear. Melatonin might be more beneficial for older adults who could be melatonin deficient.
• Jet lag. Evidence shows that melatonin can improve jet lag symptoms, such as alertness and daytime sleepiness.
• Shift work disorder. It's not clear whether melatonin can improve daytime sleep quality and duration in people whose jobs require them to work outside the traditional morning to evening schedule.
• Sleep disorders in children. Small studies have suggested melatonin might help treat sleep disturbances in children with a number of disabilities. However, good bedtime habits are usually recommended as an initial treatment. Talk to your child's doctor before giving melatonin to a child.

Research suggests that melatonin might reduce evening confusion and restlessness in people with Alzheimer's disease, but it doesn't seem to improve cognition.

Melatonin taken orally in appropriate amounts is generally safe. Melatonin can cause:

• Headache
• Dizziness
• Nausea
• Drowsiness

Less common melatonin side effects might include short-lasting feelings of depression, mild tremor, mild anxiety, abdominal cramps, irritability, reduced alertness, confusion or disorientation.

Because melatonin can cause daytime drowsiness, don't drive or use machinery within five hours of taking the supplement.

Don't use melatonin if you have an autoimmune disease.

Possible drug interactions include:

• Anticoagulants and anti-platelet drugs, herbs and supplements. These types of drugs, herbs and supplements reduce blood clotting. Combining use of melatonin with them might increase the risk of bleeding.
• Anticonvulsants. Melatonin might inhibit the effects of anticonvulsants and increase the frequency of seizures particularly in children with neurological disabilities.
• Blood pressure drugs. Melatonin might worsen blood pressure in people taking blood pressure medications.
• Central nervous system (CNS) depressants. Melatonin use with these medications might cause an additive sedative effect.
• Diabetes medications. Melatonin might affect sugar levels. If you take diabetes medications, talk to your doctor before using melatonin.
• Contraceptive drugs. Use of contraceptive drugs with melatonin might cause an additive sedative effect and increase possible side effects of melatonin.
• Cytochrome P450 1A2 (CYP1A2) and cytochrome P450 2C19 (CPY2C19) substrates. Use melatonin cautiously if you take drugs such as diazepam (Valium, Valtoco, others) and others that are affected by these enzymes.
• Fluvoxamine (Luvox). This medication used to treat obsessive-compulsive disorder can increase melatonin levels, causing unwanted excessive drowsiness.
• Immunosuppressants. Melatonin can stimulate immune function and interfere with immunosuppressive therapy.
• Seizure threshold lowering drugs. Taking melatonin with these drugs might increase the risk of seizures.