How Melatonin Supplements May Be Causing Your Excessive Daytime Sleepiness

How Melatonin Supplements May Be Causing Your Excessive Daytime Sleepiness
How Melatonin Supplements May Be Causing Your Excessive Daytime Sleepiness

My Melatonin Journey

About three years ago, I was prescribed melatonin at a dosage of 0.3 mg per night to help with my sleep. Initially, the medication made me sleepy but did not consistently help me fall asleep. As a result, my dosage was increased to 1 mg, and a year ago, it was further increased to 2 mg. Over the last 12 months, I experienced a slow onset of daytime brain fog, which became a serious problem around six months ago. We investigated various potential causes, such as the CPAP treatment I had been on for a few years, monitored blood oxygen levels during sleep, vitamin B12 deficiency, and other blood tests, but nothing came back as the culprit to explain the sudden onset of daytime exhaustion.

My work suffered, my sleep quality declined, and I felt like I was at the end of the road until I decided to try one final thing. I lowered the dosage of melatonin back to 0.3 mg per night. Within a few days, I started feeling more awake upon waking, my work improved significantly, and now, a few weeks in, I feel much more alert and productive each day.

Understanding Melatonin and Its Effects

Melatonin is a hormone produced by the pineal gland in the brain that regulates the sleep-wake cycle. It is often used as a supplement to treat insomnia and other sleep disorders. While generally considered safe for short-term use, the effects of long-term melatonin supplementation are less well understood.

The Hidden Effects of High-Dosage Melatonin

Several studies suggest that excessive melatonin supplementation can lead to various side effects, including daytime sleepiness and brain fog. According to a study published in the Journal of Clinical Endocrinology & Metabolism, high doses of melatonin can lead to elevated blood levels of the hormone, which can affect the body’s internal clock and lead to feelings of drowsiness during the day .

Another study in the Journal of Sleep Research found that while melatonin can help initiate sleep, higher doses do not necessarily improve sleep quality and can lead to residual drowsiness the following day . This residual effect might be more pronounced in individuals who take higher doses of melatonin over extended periods, as the body may not metabolise the hormone efficiently.

Why Wasn’t Melatonin Suspected Sooner?

It may seem obvious to some that melatonin could be the culprit, but it’s important to note that melatonin is often considered a mild sleep aid with an action duration of about eight hours. Given past issues with sleep, melatonin was not initially suspected as the primary cause of my daytime exhaustion.

The Importance of Finding the Right Dosage

My experience highlights the importance of finding the right dosage of melatonin. The National Center for Complementary and Integrative Health suggests that lower doses of melatonin are often just as effective as higher doses for improving sleep onset and quality, and they carry a lower risk of side effects .


If you are experiencing excessive daytime sleepiness and are using melatonin supplements, it may be worth re-evaluating your dosage. As my story illustrates, a higher dose is not always better and can lead to unintended consequences. Always consult with a healthcare provider before making changes to your medication or supplement regimen.


  1. Journal of Clinical Endocrinology & Metabolism: High doses of melatonin
  2. Journal of Sleep Research: Melatonin and sleep quality
  3. National Center for Complementary and Integrative Health: Melatonin and its effects

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