Melatonin

What is melatonin?

Melatonin is a natural hormone which plays an important role in regulating the body’s circadian rhythm, otherwise known as the sleep/wake cycle.[1] Melatonin production is at its highest at night, typically between the hours of 11pm and 3am, dropping off significantly during the day. Melatonin production is also affected by the seasons, with the hormone being produced earlier in the darker winter months and later in the summer.[2]

In this way, melatonin helps to promote sleep at night and wakefulness during the the day. The hormone’s function has led it to being nicknamed the sleep hormone.

How is melatonin produced and controlled?

The majority of melatonin is produced in the pineal gland of the brain, though smaller quantities are also made in other tissues of the body. Melatonin is released into the bloodstream and circulates throughout the body, where its presence is detected by receptors. These receptors then signal to the body that it is time to sleep.

The production of melatonin is controlled by the circadian clock, which is located in the suprachiasmatic nuclei region of the brain. This is a tiny region of the brain in the hypothalamus, situated directly above the optic chiasm. The suprachiasmatic nuclei region is connected to the pineal gland through the nervous system.

The circadian clock is regulated primarily by light received through the eyes, which tells it when and when not to signal for melatonin production. The circadian clock conveys whether it is light or dark outside to the rest of the body; information which accordingly sets off various functional processes, including the body’s sleep-wake timing, blood pressure regulation, seasonal reproduction (reproductive cycle) and core temperature regulation.[3]

The body’s natural production of melatonin occurs when it is dark. Accordingly, melatonin levels typically begin increasing in the late evening, and maximum melatonin levels are usually reached between 2:00 and 4:00 a.m. Levels of melatonin decline slowly thereafter, becoming barely detectable in the daytime. This cycle repeats every day; the body’s rhythm is kept to an approximate 24 hour cycle by the circadian clock, which roughly correlates with the light/dark cycle of nature.[3]

What are melatonin supplements used for?

Melatonin is also available in synthetic form, typically as a capsule. Synthetic melatonin is able to reset the body’s circadian rhythm and bring on feelings of tiredness, making it a commonly prescribed supplement for those experiencing:[4][5]

  • Insomnia or jet lag
  • Benzodiazepine or nicotine withdrawal, facilitating a calmer tolerance of the withdrawal period
  • Cancer adjuvant care (a care-plan alongside treatment for cancer)[6]
  • Headaches, as a preventative medication
  • Shift-work disorder
  • Sleep disorders
  • Thrombocytopenia, which may be caused by chemotherapy
  • Winter depression
  • Dyskinesia (a disorder in which people experience uncontrolled, involuntary movement)

Taken as a supplement, synthetic melatonin mimics the effects of the naturally produced version of the hormone. Supplementary melatonin is principally used by those experiencing insomnia, those with jet lag and those with delayed sleep phase syndrome (when the circadian rhythm is out of sync with the day/night cycle). However, it is important to note that the use of melatonin supplements does not guarantee the ability to sleep and that a healthcare professional should always be consulted before beginning use.[7]

Good to know: Melatonin will not be prescribed to treat insomnia if a cause can be identified. In all cases where a medical, mental or environmental cause for insomnia is discerned, the causal issue(s) will be addressed as a first line treatment.

When not to take melatonin supplements

Pregnant or breastfeeding women should not take melatonin, nor should those with an autoimmune disorder, a seizure disorder or depression. If a person is younger than 20 years old, the use of melatonin supplements should be discussed with a doctor prior to taking them. Those with high blood pressure, impaired liver function or diabetes should always consult a doctor before beginning to use melatonin.

Melatonin may react with other medications. For this reason, is always recommended that a person check with their doctor before using melatonin supplements at the same time as taking other medications. In particular, a person should be closely monitored in case of drug interactions if they are using medications including:

  • Anticoagulant (anti blood-clotting) medication
  • Concurrent immunosuppressive treatment
  • Any medication used on a chronic (long-term) basis

People using melatonin should stop if the supplement does not work after a week or two of use. Generally, melatonin supplementation should be considered a short-term rather than a long-term solution to problems with sleep. People experiencing recurrent or severe sleeping disorders should seek the advice of a doctor, who will present other therapeutic options in the event that melatonin supplementation does not provide relief.

How to take melatonin

In the US, melatonin is available without a prescription from pharmacies and health food stores. In the EU, a doctor’s prescription will be required in all cases. Elsewhere, a doctor’s prescription may also be required, to ensure that the supplement is safe for the person to use and to diagnose any possible underlying conditions that are causing sleep problems.

Doses of melatonin should be somewhere between 0.5 and 5 mg, with research suggesting that there is little difference in the effectiveness of a larger dose. Most melatonin supplements come in slow release form, meaning they work gradually throughout the night, mimicking how the body naturally releases the hormone.

It is generally recommended that melatonin should be taken one or two hours before bed, though some people will experience a wave of tiredness roughly 20 minutes after taking it. If using to combat jet lag, the supplement should be taken close to bedtime at the destination.[8]

Melatonin side-effects

Melatonin is generally described as safe when taken in the short-term. Despite this, the advice of a doctor should always be sought before beginning to use the supplement.

Possible side-effects of taking melatonin supplements may include:[9]

  • Drowsiness during the day (daytime fatigue)
  • Abdominal cramps
  • Decreased alertness
  • Irritability or feelings of depression (transient)
  • Dysphoria in patients who are already depressed
  • Stomach pain
  • Headache
  • Dizziness

Immediate medical attention should be sought if any of the following signs occur, as they may be signs of an allergic reaction:

  • Difficulty breathing
  • Hives
  • Swelling of the face, lips, tongue or throat

Other signs that a person may require medical attention include:

  • Dysphoria (profound state of unease or dissatisfaction)
  • Unresponsiveness to stimuli

  1. National Sleep Foundation. “What is Circadian Rhythm.” Accessed September 15, 2017.

  2. Drugs. “Melatonin.” February 26, 2017. Accessed September 15, 2017.

  3. You and Your Hormones. “Melatonin.” January, 2015. Accessed September 18, 2017.

  4. Melatonin dosing: herbs/suppl.” MedScape. 2018. Accessed: 21 March 2018.

  5. NCBI. “Dietary factors and fluctuating levels of melatonin.” July 20, 2012. Accessed September 18, 2017.

  6. Journal of Clinical Oncology. “Melatonin as adjuvant care with and without chemotherapy: A systematic review and meta-analysis.” 2010. Accessed: 17 April 2018.

  7. John Hopkins Medicine. “Melatonin for Sleep: Does it Work?” Accessed September 18, 2017.

  8. Sleep Health Foundation. “Melatonin.” Accessed September 18, 2017.

  9. Drugs. “Melatonin Side Effects.” Accessed September 18, 2017.