Melatonin – How Long Does It Last In The Body?

Melatonin is a naturally occurring compound that promotes sleep. The hormone is available as an over the counter sleeping medication. The sleeping aid stays in the body for a period of 2.5 hours to 10 hours. This is however dependent on the dosage as well as other factors. However, many people looking to use melatonin for sleep wonder about ‘how long does melatonin last’. In this article, we will look at melatonin, how long it lasts in the body as well as the drug prescriptions.

What is melatonin?

Melatonin is produced by the pineal gland in the body. During daylight, retina absorbs light and sends a signal to the pineal gland to stop producing melatonin. When the night comes, light goes and a signal is sent to the pineal gland to start producing melatonin.

Melatonin acts on the Default Mode Network of the brain when a person is not engaged in any mental or physical activity. The effects of melatonin on this region promote sleep in the body. Although melatonin is produced naturally in the body, it is also available as an over the counter medication for people who have sleeping challenges. The medication can be used by:

  • People who suffer from jet lag
  • Night shift workers
  • Visually impaired and blind people
  • People suffering from dementia

 How long melatonin lasts in the body

Over the counter melatonin is considered as a dietary supplement and can be used together with multivitamins and minerals. Melatonin has a half life of 1 to 2 hours depending on the medication and formulation. Half life is the amount of time the body takes to metabolize half the dose of melatonin tablets. On the other hand, the body takes about 5 half-lives to eliminate the drug from the system. This means that the drug will last in the body for a period of between 4 and 10 hours. Again, this depends on both dosage and formulation.  

‘After along and haul flight, I took melatonin at 10 am and by 12 noon, it had knocked me out’ says john, a traveler from New York.

How long do the effects of melatonin begin to show?

One of the things that you need to note about melatonin is that it is readily absorbed by the body. When absorbed, melatonin levels peak within one hour. This is the reason why you start feeling drowsy after taking the medication. Melatonin responds differently from person to person. In some people, melatonin kicks in faster than in others. Also, the time taken for melatonin to take effect in body is also dependent on formulation.  

Many manufacturers package melatonin tablets into immediate-release capsules that instantly release melatonin into the bloodstream. On the other hand, the extended-release melatonin is released into the bloodstream at a very slow rate. This can extend over a period of several hours. However, one formulation may work better in one individual than in others. However, it is all dependent on their sleeping issues as well as how their blood is able to process melatonin.  Fast release melatonin may enable you to fall asleep fast. But on the other hand, extended-release melatonin helps you to stay asleep over the night.

There are several factors that affect how your body responds to melatonin. They include:

  • Overall health status
  • Age
  • Sleep hygiene
  • Caffeine consumption
  • Tobacco use
  • Body composition
  • Other medications that you are using

At what time should I take melatonin?

As we have seen above, melatonin takes about 30 to 60 minutes to take effect. Therefore, it is advisable for users to take medication about 30 minutes before going to sleep. It is however important to note that melatonin does not affect everyone in the same way. Therefore, you may want to start off with a smaller dose of melatonin when going to sleep but later, adjust the dosage depending on your response and sleeping habits.

It is important to avoid taking melatonin after your sleeping time. This is because the medication is going to alter your sleep wake cycle. If you do, you may fall to wake up at the right time and in the worst case scenario, cause daytime fatigue. Over time, you need to learn what works or doesn’t work in your situation. If followed correctly, melatonin can help you get enough sleep.

What are the side effects of melatonin?

Although melatonin has been classified as safe to use, some users report some symptoms such as the following:

  • Fatigue
  • Nausea
  • Dizziness
  • Headaches

If you are currently on other types of medications or are experiencing any side effects after taking melatonin, you need to talk to your doctor. The doctor will then examine your individual situation before advising on the way forward.


Melatonin is an effective cure for mild and chronic sleeping problems. As we have seen above on ‘how long does melatonin last?’ it is safe to say that melatonin takes effect from 30 to 60 minutes. Over the counter melatonin will stay in the body for a period of between 4 hours to 10 hours. However, this is based on the dosage and formulation.

You should however avoid taking melatonin past your sleeping time as it will affect the time that you wake up. Also, doing so can cause you to become sleepy during the day. For the best effect, you need to practice good sleep hygiene which will not only help you to fall asleep faster, but also keep you asleep throughout the night.