Medically reviewed on August 1, 2022 by Jordan Stachel, MS, RDN, CPT. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.
Table of contents
If you’ve ever laid awake at bedtime, unable to fall asleep, you’re not alone—sleep disorders affect upwards of 70 million Americans every year. 
Now, you may be asking yourself "Why can’t I sleep at night?" While your inability to catch good Zs may be attributed to several factors, a hormone melatonin deficiency could be the likely culprit.  In short, a melatonin deficiency is a drop in the levels of the sleep hormone known as melatonin.
Read on to learn the signs, symptoms, and causes of a melatonin deficiency, as well as how to test for this condition. That way, you can start taking steps to make your nights less restless and more restful.
Melatonin: The sleep hormone
It may surprise you to learn that scientists are still discovering precisely how we enter the Land of Nod. That said, research shows that melatonin plays a large role in helping us fall asleep. 
Released by the brain’s pineal gland, melatonin can influence the following bodily functions: 
- The circadian rhythm – Our circadian rhythm is another term for the body’s internal clock. This 24-hour cycle governs many vital processes—especially the sleep wake cycle. In other words, our circadian rhythms help regulate when we fall asleep and when we wake up. Melatonin levels are highest at night and lowest during the day.
- The menstrual cycle – Studies show that melatonin can also help regulate the menstrual cycle. 
- Brain functioning – An incredibly complex organ, the brain can lose neural connections over time. Scientists have discovered melatonin’s ability to protect these networks, as well as promote regeneration. 
While natural melatonin levels differ based on age and sex, most people have consistent melatonin levels until 40 years old. After 40, melatonin levels begin to decline, resulting in deficiencies. 
That said, melatonin deficiencies can impact people regardless of age and sex.
Causes of melatonin deficiency
Although scientists are still working to pinpoint the exact causes of melatonin deficiency, contemporary research highlights three potential factors: 
- Age and disease – As stated above, melatonin levels decrease as we age. After age 90, melatonin levels are 20% of what they are in a younger adult.  Studies also suggest that neurobiological diseases such as Alzheimer’s, schizophrenia, and dementia can contribute to decreased melatonin levels. 
- Light exposure – Responding to darkness, our pineal glands release more melatonin at night. As a result, increased light exposure—especially at night—can suppress melatonin secretion.
- Melatonin signal disruptions – Like all hormones, melatonin signals to the body that it’s time to do something—in this case, sleep. However, if your melatonin receptor is malfunctioning, melatonin signals can’t perform their roles. 
Signs of melatonin deficiency
Given melatonin’s prominent role in sleep regulation, many signs of melatonin deficiency typically involve sleep. The most common signs include: 
- Excessive daytime sleepiness
- Nocturnal awakenings
- Circadian rhythm disruptions
That said, research also suggests that melatonin deficiencies may impact non-sleep-related functions, contributing to: 
- Loss of antioxidant protection
- Acceleration of aging
- Immunological aging
- Metabolic disorders
Symptoms of melatonin deficiency
Like signs of low melatonin levels, melatonin deficiency symptoms typically manifest as a sleep disorder. The sleep disorder can, in turn, contribute to neurobiological and behavioral symptoms.
The most common symptoms of melatonin deficiency include:
- Insomnia – People struggling with insomnia, whether it’s stress induced insomnia or acute insomnia, often have a difficult time falling asleep during bedtime and staying asleep. Many insomniacs will fall asleep eventually, only to wake up during the night. A low melatonin level can disrupt a person’s circadian rhythm and sleep pattern, preventing them from entering a natural sleep wake cycle.
- Depression – Scientists have suspected a link between melatonin levels and depression for many years. Currently, the consensus among scientists is that certain depressive disorders can stem from circadian dysfunction. Low melatonin levels appear to play a large role in creating the conditions for circadian irregularities and sleep difficulties.
- Weight gain – Sleep is such a powerful bodily function that sleep problems can lead to many unexpected complications—including weight gain. While extensive studies haven’t been performed on humans, studies on rats suggest that decreased melatonin levels can contribute to weight gain, while increased levels can reverse the effects of weight gain.
The good news is that these symptoms don’t have to last forever. If you’re experiencing these signs and your healthcare provider determines low melatonin levels are to blame, they can prescribe a melatonin supplement to help remedy the deficiency.
Treatments for melatonin deficiency
If you’re wondering how to fix your sleep schedule due to a melatonin deficiency, there are options. Treating a melatonin deficiency depends on a person’s present levels of melatonin. For people requiring short-term melatonin support, healthcare providers recommend taking melatonin supplements. Many studies suggest that taking melatonin can help promote better sleep at doses as low as 0.1–0.3 mg/d. 
Healthcare providers may also recommend that you limit your exposure to light during the evenings, as well as engage in hormone melatonin substitution therapies throughout the night. 
5 reasons why you can't sleep
4 ways to handle stress-induced insomnia
Tips on how to fix your sleep schedule
- Insomnia. Cleveland Clinic. URL. Accessed August 1, 2022.
- Neurobiology, Pathophysiology, and Treatment of Melatonin Deficiency and Dysfunction. Scientific World Journal. URL. Accessed August 1, 2022.
- Melatonin. Cleveland Clinic. URL. Accessed August 1, 2022.
- Melatonin promotes regeneration of injured motor axons via MT1 receptors. Journal of Pineal Research. URL. Accessed August 1, 2022.
- Research progress of melatonin (MT) in improving ovarian function: a review of the current status. Aging. URL. Accessed August 1, 2022.