What does melatonin do?

Melatonin helps control your circadian rhythm. This is your sleep-wake cycle that happens automatically about every 24 hours.

Melatonin helps your body get ready to fall asleep. It’s not a magic potion that makes you sleepy, but it’s an important chemical change in your body that happens each day.

Your pineal gland releases the most melatonin when there’s darkness and decreases melatonin production when you’re exposed to light. In other words, you have high melatonin levels at night when you’re sleeping and less in your blood during the daylight hours.

The longer the night, the longer your pineal gland secretes melatonin. That’s why some people feel sleepy earlier or more often in winter months. In winter, there’s less sunlight in the day and it stays dark longer, so your body naturally releases more melatonin in response.

Melatonin is a chemical messenger that tells your body it’s time to relax and get ready to rest. Your pineal gland automatically releases extra melatonin around the same time every day. This usually happens when the sun goes down.

Melatonin affects cells in your brain’s hypothalamus. It tells your hypothalamus it’s time to slow activity down for the day. Once it gets the message, your hypothalamus dials back the functions it controls — like your body temperature, blood pressure and mood — to get you ready for sleep.

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In your eyes, melatonin changes your retinas to get ready for rest and being less active. Melatonin helps your retinas become less responsive to light, which helps you wind down and feel less alert. When there’s more natural light the next morning, your retinas automatically become more active and your body stops releasing as much melatonin.

Melatonin plays an important role in making sure you get enough sleep. Your body needs that natural, chemical reminder to feel tired each night. Getting enough sleep is important for every part of your health and body, including your:

Melatonin’s biggest job is regulating your sleep-wake cycle. But it works in other areas of your body, too:

Your natural melatonin level can vary depending on your age and sex recorded at birth. Females typically have higher melatonin levels than males.

The level of melatonin your body produces changes throughout your life.

Newborn babies don’t produce their own melatonin. Before birth, they receive melatonin from the placenta. After birth, they can receive it through breast milk or formula. Babies develop a melatonin cycle when they’re 3 to 4 months old.

Melatonin levels are highest in kids and teens right before starting puberty. After puberty, there’s a steady decrease in melatonin levels until it evens out in your late teens. The level is stable until around age 40, followed by a natural decline for the rest of your life.

You may never know your melatonin level if you don’t experience any symptoms or need tests to measure it. If you do need a melatonin test, your healthcare provider will let you know if your levels are within normal ranges.