What is Melatonin? Benefits, Dosage, and Side Effects

Do you have trouble sleeping at night? Chances are you may have tried melatonin supplements. This natural sleep aid is often used by people who suffer from insomnia and jet lag.

Interestingly, the benefits of melatonin are not restricted to sleep. Recent research has uncovered many additional benefits of melatonin like improvement in heart health, fertility, preventing cancer and better immunity.


Read on to learn more about the benefits of melatonin, its correct dosage, and its side effects.

What is melatonin?

Melatonin is an endogenous hormone produced in the pineal gland (1). Shaped like a pine cone, the pineal gland is located just above the middle of the brain.

Melatonin is also called the ‘hormone of darkness’ as it is responsible for regulating the body’s circadian rhythm and helps manage the natural sleep cycle (2).

Darkness triggers the pineal gland to release melatonin, which makes you sleepy. The levels of melatonin stay high through the night; this helps you stay asleep.

These levels begin to wane when the sun comes up and reduce drastically during day time.

Helping us sleep well is not the only job of this hormone. It also helps to boost heart health, improve immunity, reduce oxidative stress, decreases menopause symptoms, and improves eye health.

It helps to regulate body temperature, blood pressure and hormone levels (3).

Melatonin levels naturally decrease as we age, which is why it becomes more difficult to fall asleep as we age. Other factors like stress, smoking, exposure to too much light at night and not getting enough sunlight during the day can also affect melatonin production.

Taking melatonin supplements can help counter the low levels of this hormone. These supplements come as pills, liquids, and lozenges.

Benefits of melatonin

1. Supports better sleep

Melatonin helps people with insomnia and other sleep issues to sleep better. This natural sleep aid regulates the natural circadian rhythm of the body for people with disrupted circadian rhythms like people who have jet lag or are working the night shift.

According to a 2016 study, daily intake of oral melatonin two hours before bedtime improves sleep induction and quality in cancer patients with insomnia (4).

According to a meta-analysis of 19 studies involving 1683 subjects, melatonin improves the quality of sleep, increases total sleep time and reduced the time it took to fall asleep (5).

Melatonin is also helpful for people who suffer from jet lag. An analysis of ten trials was done to assess the effectiveness of oral melatonin for alleviating jet lag after traveling across various time zones.

Nine out of these ten trials found that melatonin, taken close to bedtime at the destination, decreases jet lag from flights crossing five or more time zones (6).

Melatonin also has lesser side effects as compared to other sleep medications.

2. Improves eye health

Melatonin is rich in antioxidants that prevent cell damage and keep eyes healthy. This hormone helps improve eye health as it prevents the death of cone cells that help identify the color.

It also protects the cells that make eye pigments and enhances the functioning of nerve cells that are crucial for vision. According to a 2005 study, 100 people with AMD, were given 3 mg melatonin orally for 6 to 24 months.

The results showed that melatonin protects the retina and delays macular degeneration with no significant side effects (7).

Melatonin also decreases the elevated pressure in the eye caused by glaucoma (8).

3. Strengthens the immune system

Researchers have known about the relationship between melatonin and the immune system for decades. While blood cells, which play an essential role in the immune function, have melatonin receptors.

Melatonin stimulates the release of cytokines that help attack the invading infection.

Melatonin also acts as an anti-inflammatory and helps prevent the damage caused when the immune system of the body attacks its tissues.

According to a 2013 study, melatonin acts as an immunological buffer because it serves as an immunostimulant under immunosuppressed conditions, and provides an effective early immune response against viruses and parasites (9).

Melatonin is highly beneficial for aged individuals as it has potential therapeutic value to enhance their immune function. A recent study found that when old mice were given melatonin at night, they began producing more cytokines and other immune molecules (10).

4. Helps prevent cancer

Melatonin is classified as a cytotoxic hormone, which means that it has a toxic effect on disease-producing cells. Melatonin also suppresses tumors of many kinds of cancers, including breast cancer.

According to the researchers from the Henry Ford Hospital in Detroit and Foundations for Research Support of the State of Sao Paolo, melatonin may have the potential to slow the growth of breast cancer tumors (11).

According to the American Cancer Society, when melatonin is combined with certain anti-cancer drugs, it suppresses the growth of some cancer cells.

During another study, women with breast cancer who were taking tamoxifen but not seeing any improvement were given melatonin. This treatment caused the tumors to shrink in 28 percent of the women.

Studies have also shown that men with prostate cancer have lower levels of melatonin. Melatonin helps block the growth of prostate cancer cells according to test tube studies.

According to a study by the University of Texas Health Science Centre, when prostate cancer cells are treated with pharmacological concentrations of melatonin, it inhibits the growth of prostate cancer cells (12).

5. Decreases menopause symptoms

According to a new study, menopausal women can benefit by taking melatonin to alleviate some of their symptoms. Melatonin production decreases as we age, particularly during the peri-menopausal period.

So, supplementing with this hormone helps improve sleep, mood and general well-being in menopausal women.

According to a study by Menopause Center, Madonna Delle Grazie Health Institute, Rome, when perimenopausal and menopausal women in the age group of 42 and 62 years took 3 mg melatonin from three to six months, they reported a significant improvement in mood and mitigation of depression (13).

6. Reduce symptoms of seasonal depression

Seasonal affective disorder (SAD), also known as seasonal depression or winter blues is a condition that is known to affect 20 percent of the adults in the US (14). Research indicates that it is caused by the changes in the circadian rhythm caused by seasonal light changes.

Since melatonin plays a vital role in regulating circadian rhythm, it could be used to treat symptoms of SAD. According to a 2006 study, when researchers gave low-dose melatonin to patients with SAD, it helped reduce the symptoms (15).

7. Protects against heart disease

Several studies have shown that melatonin has cardioprotective properties (16). The anti-inflammatory and antioxidant effects of melatonin help lower blood pressure and cholesterol.

According to a 2012 study, melatonin’s direct free radical scavenger activity is responsible for its cardioprotective properties (17).

8. Increases levels of human growth hormone

Human growth hormone (HGH) is primarily known to promote growth in children and adolescents, but it also has critical metabolic functions throughout adult life.

Human growth hormone (HGH) also helps in increasing strength and muscle mass.

Studies have found that melatonin can increase the levels of HGH in men. During one study, male volunteers were given melatonin in doses of .05 mg or .5 mg or placebo. The results showed that both these doses stimulated growth hormone release (18).

9. Fibromyalgia pain relief

According to some studies, melatonin may be useful in dealing with fibromyalgia pain. Since most patients with fibromyalgia have sleep problems and fatigue, melatonin is thought to help relieve these symptoms.

During a clinical study that involved 101 fibromyalgia patients, it was observed that the patients that took melatonin alone or with antidepressant fluoxetine experienced a significant reduction in their symptoms (19).

10. Treats stomach ulcers and heartburn

Many studies have shown that melatonin is effective in treating stomach ulcers and heartburn.

A study by Department of Gastroenterology, Medical University of Lublin, Poland, found that taking melatonin and tryptophan and conventional medicine for acid reflux, helped heal stomach ulcers caused by H. pylori (20).

During another study, patients with GERD were given, melatonin,  omeprazole, and melatonin along with omeprazole. The results showed that melatonin alone or in combination with omeprazole helped reduce heartburn (21).

11. Help reduce symptoms of tinnitus

Tinnitus is a health condition that is characterized by the perception of sound in one or both of your ears when there is no actual sound present in the environment.

In this condition you may hear noises like ringing, whooshing, humming or buzzing. Melatonin helps in treating symptoms of tinnitus and enables you to sleep.

According to a 1998 study, when patients of tinnitus were given 3 mg of melatonin for 30 days, they reported a significant improvement in tinnitus (22).

12. Reduces bladder dysfunction

Melatonin helps combat age-induced bladder dysfunction by reducing oxidative stress. It also helps relieve issues like overactive bladder by limiting bladder contractions and inducing relaxation.

According to an article published in Current Urology, melatonin dysfunction can lead to bladder dysfunction (23).

Another study showed that melatonin increases bladder capacity and reduces frequent nightly voiding (24).

How to take melatonin?

Melatonin is considered safe and is available over-the-counter in many pharmacies and health supplement stores. It is available as a pill, capsule, as a liquid and even as a spray. It is also available as lozenges.

Melatonin can also be applied topically. Researchers have recently discovered that melatonin can penetrate the outer layer of the skin and reinforce the skin’s capacity for repair, renewal, and revitalization during the night (25).

It is important to note that the US Food and Drug Organisation does not regulate melatonin. So it is recommended that you purchase it from a reputable source.

Correct dosage

There is no recommended dosage for melatonin. The effects of this hormone can vary from person to person, so you may have to adjust your dosage accordingly. It is always best to start from the lowest possible effective dose.

The dosage mentioned here has been studied in scientific research –

  • Trouble falling asleep: From 0.3 to 5 mg daily for up to 9 months
  • Sleeping issues in people with sleep-wake cycle disturbance: 2 to 12 mg taken at bedtime for up to 4 weeks
  • Sleep disorders in blind people: 0.5 to 5 mg daily before bedtime for six years
  • Endometriosis: 10 mg for eight weeks
  • Jet lag: From 0.5 mg to 8 mg at bedtime taken on the day of the arrival of the destination, to be continued for 2 to 5 days

Side effects and interactions

Research shows that melatonin is safe, non-toxic and non-addictive when taken by mouth. It can be taken safely for up to two years (26).

Some of the most commonly reported side effects associated with melatonin include nausea, headaches, dizziness, day time sleepiness, stomach cramps, short-term depression, irritability, and decreased libido.


Melatonin can also cause breast enlargement and reduced sperm count in men.

Pregnant and nursing women should not take melatonin without the supervision of the actor.

Melatonin can also interact with certain medications like blood pressure medications, antidepressants, blood thinners, birth control pills, beta-blockers, non-steroidal anti-inflammatory drugs, steroids, and immunosuppressant medications.

Consult with your doctor before taking melatonin if you are taking any of these medications.

Final thoughts

Melatonin is responsible for regulating the body’s circadian rhythm and helps manage the natural sleep cycle. It also improves eye health, strengthens the immune system, reduces symptoms of seasonal depression, prevents cancer and treats stomach ulcers and heartburn.

Melatonin supplements are available in pill, capsule, liquid and lozenge form over the counter at pharmacies. These supplements are generally considered safe and non-addictive.

However, in some cases, they can cause side effects like nausea, headaches, dizziness, day time sleepiness, stomach cramps, short-term depression, irritability, and decreased libido.


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