How Long Does Melatonin Stay In Your System?

Sleep aids sometimes don’t last for the entire amount of time you’d like to sleep. However, in most cases, like with melatonin, they usually don’t need to! 

Once you achieve help falling asleep and can reliably stay asleep for the first few hours, your body should naturally carry out the rest of your sleep cycle for as long as you’d like. This, of course, can vary based on a few factors. 

Melatonin: How Does It Work?

Melatonin is a hormone created by the pineal gland in your brain that is responsible for helping your body’s circadian rhythm flowing smoothly. 

The circadian rhythm is also known as your body’s internal alarm clock, as it keeps a normal sleep and wake pattern, as well as regulates whatever changes your body goes through in a 24 hour period. 

However, there are some people who don’t produce enough melatonin naturally and need the use of a melatonin supplement to help regulate their circadian rhythm. 

Some factors that can lead to low melatonin levels include:

  • High levels of stress
  • Smoking
  • Drinking too much alcohol 
  • Old age
  • Being exposed to too much blue light throughout the day (computers, televisions, cellphones, etc)
  • Not getting enough natural light

In addition, there are some people who need extra melatonin as a way to re-start or correct their circadian rhythm because of actions that have altered it.

These people include:

  • Night shift workers
  • People with jet lag
  • People with sleeping disorders (insomnia, sleep apnea, etc)

Melatonin works by binding receptors in your body, leading to lowered dopamine levels and a less alert, more relaxed feeling flowing through your body. This helps your body realize it’s starting to get to be around the time to sleep. 

Additionally, melatonin is also a natural antioxidant and can be beneficial for overall ear and eye health, among other things. 

How Long Does Melatonin Work For?

Melatonin won’t stay in your system for an entire night’s rest, but it can help aid you in falling asleep and help you to initially stay asleep. 

If you would like to target a specific time, there are even different types of melatonin to pick from for that. 

Regular Melatonin

Regular melatonin won’t stay in your system for too long. The time it takes your body to break it down is around 30-40 minutes. Afterwards, it lasts in your body for up to four hours, but that can depend on a few factors

Some of these factors include:


Older people have shown to hold melatonin in their system longer than younger people. Sometimes this also can be attributed to why senior citizens feel more side effects than younger people -- especially daytime drowsiness. 


Those who are of a heavier weight, around 250 pounds or heavier, may not feel the effects of melatonin as much as people of a lower weight. This can be from a few factors, but the main one seems to be because the medication takes a longer time to dissipate. Unfortunately, dosing for medication isn’t always one size fits all. 

Other Medications

Other medications can affect how you process melatonin and how effective it is for you. It is something to be very careful about, as some medications can provide a harmful mix to you when combined with melatonin. 

Caffeine and Other Stimulants

Stimulants like caffeine can mess with how long melatonin lasts and how it works to begin with. 

Extended Release Melatonin

Extended release melatonin is released more slowly and gradually into your system. Therefore it’s better for staying asleep, rather than for falling asleep. 

It has also shown to be the more effective melatonin choice for people 55 years old or older, showing significant improvement in sleep quality. 

Should You Take Melatonin?

Melatonin can be very beneficial for a wide variety of people experiencing sleep issues. However, there are some demographics who should not take it, as its use for them has not been studied thoroughly enough, or they should only take it under advisement from a doctor. 

Some of these people include:


Some children have been approved to take melatonin under specific guidance of their pediatrician, but due to the lack of research on how melatonin affects growth and puberty, children are not advised to take it. 

Pregnant or Breastfeeding Women

During pregnancy, women’s natural hormone levels vary a lot with the different stages of being pregnant. This is normal, and needs to happen. Therefore, introducing additional melatonin can alter their natural melatonin production and cause issues. Additionally, although there hasn’t been enough conclusive research to prove this, there is some concern about the melatonin passing to the fetus through the pregnant mother and to the baby through the breastfeeding mother, possibly interfering with their growth.

People Taking Medications That Can Interact with Melatonin.

Melatonin supplements can unfortunately interact with a variety of different medications (namely blood thinners, autoimmune medications, seizure medications, and more), and therefore using both is highly discouraged. This is because the combination of the two can create an inhospitable environment for them to work, rendering them not as useful or in some cases, cancelling out the effects of one or both of them altogether. If you are worried that your medication might interact with melatonin, it is advisable to ask a doctor first if the combination is a safe and promising one for you. 


Alcohol and melatonin don’t mix well, even though they seem like they should. Both can help encourage sleep initially, but together they can alter your liver function, make you dizzy and nauseous, make you anxious, and can cause drowsiness outside of the window you’re looking for. Additionally, although alcohol initially can help people feel more sleep, it actually messes with your circadian rhythm and can make staying asleep hard. As a result, people who are alcoholics naturally have lower melatonin production. But no, you shouldn’t try to supplement that melatonin back with a pill, for all the reasons listed above. 

Older Adults

The elderly can take melatonin, and in many cases, doctors recommend it. However, there is a risk of daytime drowsiness in the elderly, as melatonin has shown to last longer in their systems than for other people. Therefore, it is very important for senior citizens to heed the advice that everyone taking melatonin should follow -- do not operate a vehicle or heavy machinery for at least five hours after taking melatonin. 

To Conclude

Melatonin as a supplement can last in your system for up to four hours at a time, but it can depend on who you are and how you’re built, as well as what type of melatonin it is -- extended release versus normal melatonin. 

Which is best for you can depend on a number of factors, but as for any supplement or medication, you should be sure to research the brand you’re using and any side effects, as well as take advantage of guidance from your doctor.