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Melatonin Supplements for Sleep: Benefits vs. Side Effects

Genes Mentioned
Note: melatonin supplements are not regulated by the FDA, so quality and dose consistency can vary. The CDC has expressed some concern about melatonin supplements, especially for workers using them to adjust to circadian rhythm disrupting overnight work. Why is melatonin a popular sleep supplement and how does it help us sleep?

What role does melatonin play in sleep?

The brain’s pineal gland makes the hormone melatonin when darkness sets in. 1 In a healthy circadian rhythm, levels of the stress hormone cortisol peak in the morning and wane at night as melatonin, the sleep promoting hormone does its thing. Cortisol gets a bad rap, but it gets us up and going in the mornings. The trouble begins when those levels don’t naturally come down at night. Melatonin is the hormone our bodies release to signal it is time to hop in bed and get a good night’s sleep. As the day progresses and the sun sets, melatonin should naturally take the wheel. However, notice I mention melatonin’s role putting us to sleep in the context of the circadian rhythm, which is our natural clock regulated by light and and dark. Darkness brings on melatonin production, but we live in a chronically illuminated world. The blue light emitted from our phones, televisions, and LED lamps sends a signal that it’s always daytime. When nighttime does settle in, it’s polluted by technology. The results? Our bodies struggle to get the melatonin we need to sleep well. This is why many of us turn to melatonin supplements, but do they work, and if so, at what cost?

Do melatonin supplements improve sleep?

The best evidence seems to indicate that melatonin can indeed help with sleep onset, meaning taking a melatonin supplement can give you the warm, fuzzy, sleepy feeling you’re looking for come bedtime. Whether you stay asleep is another story. Let’s look at the evidence for the three core areas of research on melatonin supplements and sleep: sleep onset, sleep quality, and total sleep time. A meta-analysis of 19 studies found that melatonin (usually in relatively large doses of between 2-5 mg) helped improve all three categories, but by how much?

Sleep onset latency (how fast you fall asleep)

Studies demonstrate a clear benefit from taking melatonin supplements on how fast you fall asleep. Those taking melatonin fell asleep on average 7-10 minutes faster than placebo, with the benefits increasing from larger doses. 2

Total sleep time

In the meta-analysis of 19 melatonin studies, total sleep time was increased by an average of 8 minutes in the supplement group vs. the placebo group. 2 The studies did show a clear benefit for taking melatonin, but let’s be real, 8 minutes of extra sleep does not add all that much to the “bright eyed and bushy tailed” factor for most of us. Frankly, a review of the research led me to believe that supplemental melatonin is vastly overrated as a sleep supplement.

Sleep quality

Many of the studies in the meta-analysis showed some benefit for sleep quality as well. This is the most malleable of the metrics studied because sleep quality is the subjective assessment of each individual after they wake up. In essence, it’s the scientific equivalent of the age old question “good morning, how did you sleep last night?” 3

Melatonin vs. popular sleep medications

Melatonin doesn’t outperform popular prescription sleep medications, like Ambien, when measuring sleep onset, quality, and time. The prescription medications are more effective, however, melatonin isn’t thought to be habit forming, which is a major problem with sleep drugs. 2

Melatonin side effects

According to Penn Medicine, melatonin supplements can cause side effects such as:
  • headaches,
  • dizziness,
  • nausea,
  • irritability,
  • or daytime drowsiness
  • disrupted sleep patterns

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My experience with melatonin supplements


My experience with melatonin tracks very nicely with the scientific research, both in terms of sleep onset benefits as well as common side effects. I do notice that taking melatonin 30-60 minutes before my planned bedtime, as recommended by Penn and other medical authorities, does improve the speed with which I fall asleep. There is an undeniable drowsiness that takes over, which as I mentioned above, is a major benefit when a stressful day threatens to keep you up a little longer than you’d like. Supplements like lysine, lemon balm, magnesium, L-theanine, and CBD seem to have a much greater benefit for my sleep (and heart rate variability) than does melatonin, which puts me to sleep, but doesn’t help me stay there. If I take too much melatonin, I experience many of the side effects reported by the University of Pennsylvania.

Side effects

Taking melatonin at doses north of 1mg for even two days in a row leaves me with a residue of grogginess and low mood that can last the better part of the day. If I take large doses, I will sometimes experience strange dreams. The dreams don’t bother me. Melatonin is a supplement I would turn to to reset my circadian rhythm after an overseas flight, but not with any regularity in my day to day life. One possible exception is using micro-doses of melatonin a couple times a week in combination with sleep supplements that offer greater benefit for me. My sweet spot seems to be about 0.5mg, and even then, I limit that dose to once or twice a week when I feel like I have over caffeinated and may have trouble getting to sleep quickly.

Final thoughts

Unless I take very small staggered doses, the side effects of melatonin outweigh the benefits for me. Although an estimated 3 million Americans take melatonin every year, the research looking at proven benefits is actually much thinner than you would think. Because the body makes its own melatonin, there is a case to be made that, rather than popping a pill, a better strategy for increasing melatonin production would be to mimic the natural rhythms of light and dark inside your home. Light and dark cycles are by far the most important factor in synchronizing our ability to make melatonin “in-house.” 4 This means turning off most lamps, computers, and tablets at least two hours prior to bed and being vigilant with light pollution inside of the bedroom is the best way to ensure your body is making adequate melatonin. If the body gets exposure to a dark environment, nature will take over. There is some concern that over supplementing with melatonin could prevent the body from effectively making its own. For more on the genetics of melatonin metabolism and variability in melatonin receptor activity, check out our MTNR1B gene page.

Dr. Aaron Gardner, BSc, MRes, PhD

Dr. Aaron Gardner, BSc, MRes, PhD is a life-scientist with a strong background in genetics and medical research, and the developing fields of personalized medicine and nutrition. Read his full bio here.

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