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If you've used melatonin to assist with sleep only to wake up feeling drowsy, there's a reason for that. Knowing how long melatonin stays in your system—along with why a melatonin hangover occurs—is a big factor in using it properly.
Melatonin has a relatively short elimination half-life of around 1 to 2 hours, depending on the product used. However, getting the full picture of melatonin doesn't just involve its half-life, as there are several factors that help determine how long melatonin remains active within your body, as well as if you might experience effects the next day.
The half-life of melatonin is between 20 and 40 minutes, meaning half of the initial dosage in the body is eliminated after that amount of time. Some sources indicate melatonin has a half-life of slightly longer duration, citing studies between 40 to 60 minutes. This variation may come from differences in metabolism due to differences among the study participants and the specific product used.
Generally, it will take a drug approximately 4 to 5 half-lives to be considered fully eliminated. In practice, that means melatonin will stay in your body for something close to 5 hours. Studies have supported this timeline as well. For example, one small study examined melatonin levels in blood samples from a group of healthy male adults after taking an oral 10 milligram dose of the supplement. The researchers found that on average melatonin levels dropped to zero after five hours.
If you need additional options or struggle to maintain a proper sleep schedule, have a look at our guide to learn how to fall asleep faster and strategies that go beyond melatonin.
Your body has sophisticated biochemical pathways to process melatonin that help explain why timing and dosage are so important for avoiding morning drowsiness.
In humans, the pineal hormone melatonin is principally metabolized to 6-hydroxymelatonin, which is further conjugated with sulfate and excreted in urine. It is primarily metabolized by the liver enzyme CYP1A2 and to a lesser extent by CYP1A1, CYP2C19, and CYP1B1.
CYP1A2 is an important catalyst of the 6-hydroxylation of melatonin and therefore the primary mechanism driving the rate of systemic clearance of melatonin. All the above data provide strong experimental evidence that CYP1A2 is an important catalyst of the 6-hydroxylation of melatonin. This helps explain why some people are more susceptible to next-day morning drowsiness than others.
There are several factors you may want to consider when evaluating your own clearance of melatonin and determining whether you experience side effects of melatonin:
Caffeine Interference: Caffeine was found to increase the oral bioavailability of melatonin probably due to an inhibition of the CYP1A2 catalysed first-pass metabolism of melatonin. When caffeine was coadministered the Cmax and AUC of melatonin were increased on average by 142% and 120%, respectively. This means consuming caffeine can significantly extend melatonin's duration in your system.
Individual Genetic Variations: The effect was more pronounced in nonsmokers and subjects with the *1F/*1F genotype, suggesting that genetics may also determine the rate at which melatonin is metabolized.
Understanding these interactions is very important for those comparing melatonin vs prescription sleep aids.
The dreaded melatonin hangover is a very real feeling for many users, but it is completely avoidable with education and dosing. For the most information on this issue, you should refer to our deep dive on melatonin hangover effects.
We asked Dr. Suzanne Gorovoy, Sleep Expert, Clinical Psychologist, and Behavioral Sleep Medicine Specialist what her experience and practice in sleep science can tell us about melatonin's next-day effects. She says: "Grogginess the following morning is a classic sign of a melatonin hangover, especially when a higher dose or inappropriate timing is involved. The grogginess that occurs comes from the residual melatonin that is still in your system that keeps you feeling drowsy, even when you want to be alert."
A melatonin hangover is one of the most common side effects of melatonin. It results in drowsiness, daytime sleepiness, headaches, and in some cases, nausea. Melatonin hangovers usually happen for one of two reasons: taking too much melatonin, or taking melatonin too late in the evening.
The popular use of melatonin is to make you sleep. However, this sleepiness can carry on into the following day. Daytime sleepiness is when you feel the need to fall asleep despite wanting to be awake. Other common effects in the morning can include:
If you are experiencing ongoing fatigue in the morning, be sure to check out our article on why you wake up tired.
The secret to avoiding morning impacts is timing and amount. If you are looking for alternatives to melatonin, then be sure to take a look at our head-to-head comparison of Magnesium vs. Melatonin.
We asked Dr. Michael Grandner, Sleep Expert and Professor of Neuroscience and Physiological Sciences about optimal melatonin dosing. He says: "Lower doses of 0.5 - 3 mg are usually more effective than higher doses, and this significantly lowers the risk of next-day grogginess." Dr. Grandner's statement is in direct contrast to the "more is better" mentality, in which many people take excessive amounts of melatonin.
Scientific studies published in the Journal of Biological Rhythms and The Journal of Clinical Endocrinology & Metabolism show that a maximum shift occurred 0.5 milligrams compared to a previous study with 3 milligrams. Johns Hopkins recommends taking 1 to 3 milligrams two hours before bedtime.
As far as timing, the best time to take melatonin is about 1 to 2 hours prior to your desired sleep time, and you will want to be mindful not to take melatonin too late prior to your desired sleep time. Dr. Conroy adds that the best time to take melatonin is four to six hours before heading to bed for circadian rhythm disorders.
As mentioned, this is why it's best to take melatonin at least 8 hours before you need to wake up. This helps ensure it's out of your system by the time you wake up, which helps you avoid feeling tired or groggy in the morning.
For individuals who would like to work on timing their sleep, see our guide for tips to sleep earlier which are complementary.
The kind of melatonin formulation you choose will impact the duration of effects, and whether you feel effects the following morning.
Opting for an immediate release pill or chewable tablet may help you fall asleep faster and wake up feeling more refreshed. Typically, these will also leave the body in more of a predictable fashion, typically 4-5 hours duration.
Taking an extended release melatonin pill may make you feel more tired when you wake up, especially if you are not able to get a full eight hours of sleep. Extended release pills may also take longer to help you fall asleep. Extended-release can potentially be beneficial for individuals who have difficulty staying asleep in the night. However, extended-release melatonin may also increase the risk of negative side effects like sleepiness the next day.
If you experience nighttime awakenings, our complete guide on sleep maintenance insomnia offers effective strategies.
The lack of regulation established by the FDA leaves significant variability in melatonin products, which can influence both efficacy and adverse morning effects. Check out further information on melatonin safety warnings.
One study published by the American Medical Association in April 2023 looked at over-the-counter melatonin gummies. In these products, the actual quantity of melatonin ranged from 74-347% of the labeled quantity. Researchers found that 22 of the 25 products – 88% – were inaccurately labeled. This degree of variability makes it incredibly difficult to make predictions about the duration of effects.
A study examining 31 melatonin supplements discovered that the actual melatonin content varied widely, ranging from −83% to +478% of the labeled content. This level of fluctuation can explain why some people might experience surprise morning grogginess, even with justifiable doses.
Many personal factors influence how long melatonin will impact you, which is why we take an individualized approach to sleep coaching to tailor to differences between individuals.
Normal levels of melatonin decline with age, which can impact natural production and metabolism of melatonin supplements. Premature neonates often exhibit a prolonged half-life of melatonin compared to adults, while older adults may have a different metabolism of melatonin dose levels due to age-related reasons, such as liver function.
Clinicians should exercise caution when prescribing melatonin to patients with impaired liver functioning, as their ability to metabolize the medication may be reduced. This could lead to a prolonged half-life of melatonin and an increased risk for morning grogginess.
We asked Dr. Areti Vassilopoulos, Sleep Expert, Pediatric Health Psychologist, and Assistant Professor of Child Psychology about when morning effects become problematic. She says: "If you frequently wake up feeling groggy or impaired by melatonin, you should reconsider your dosing approach or rethink using melatonin as your sleep aid."
If you experience many effects in the morning that persist, it may be due to:
If you continue to have difficulty sleeping, you should also look into an alternative therapy option, CBT-I.
Recent research has revealed important interactions that can significantly extend melatonin's duration in your system. A study published in the British Journal of Clinical Pharmacology found that oral contraceptives increased mean melatonin AUC and Cmax values 4- to 5-fold higher in OC users than in non-OC users, whereas the weight-adjusted clearance was significantly lower in OC users.
These findings hold key takeaways for females on hormonal contraceptives in that they may be experiencing prolonged melatonin effects and elevated risk for experiencing morning grogginess. However, this study also found no significant difference in melatonin pharmacokinetics between the genotypes and no additional effect by the genotype on the OC-induced increase in melatonin exposure, suggesting that the effect of OC use was widespread and it affected all female subjects, regardless of potential genetic variations.
To minimize next-day grogginess, try our sleep hygiene tips along with melatonin specific tips:
If you would like more strategies for morning alertness, check out our blog post about how to wake up feeling refreshed.
A systematic review found that many factors can affect how quickly the body absorbs and processes melatonin, and results not only vary by study, but also on an individual basis. This variability means that it may take several tries to find your right dose and timing, so continue to work with your health care provider.
If melatonin for sleep isn't helping after a week or two, stop using it. And if your sleep problems continue, talk with your health care provider. If melatonin does seem to help, it's safe for most people to take nightly for one to two months.
For those concerned about the use of melatonin every night, check out our article about the safety of taking melatonin every night.
If you feel that melatonin is not effectively working, or it is causing issues in the morning, you could consider alternative natural sleep solutions. Our approach includes the following:
Melatonin typically lasts 4-5 hours in the system; however, morning effects may change based on dosage, timing of use, someone's metabolic rate, and product quality, among other factors. Short-term use of melatonin supplementation appears to be relatively safe for most individuals for 1-2 months. Avoiding next-day grogginess is achieved by using the lowest effective dose, proper timing for your daily routine, and ultimately getting enough sleep.
These factors help you to effectively use melatonin while still conserving your next day alertness or cognitive function. Persistent sleep issues should be determined with the help of a professional since it is typically suggestive of an underlying condition or treatment outside of supplementation.
To improve your sleep quality without the use of supplements, consider our Sleep Reset program that provides root issue resolutions through evidence-based behavioral interventions.
Dr. Shiyan Yeo
Dr. Shiyan Yeo is a medical doctor with over a decade of experience treating patients with chronic conditions. She graduated from the University of Manchester with a Bachelor of Medicine and Surgery (MBChB UK) and spent several years working at the National Health Service (NHS) in the United Kingdom, several Singapore government hospitals, and private functional medicine hospitals. Dr. Yeo specializes in root cause analysis, addressing hormonal, gut health, and lifestyle factors to treat chronic conditions. Drawing from her own experiences, she is dedicated to empowering others to optimize their health. She loves traveling, exploring nature, and spending quality time with family and friends.
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