Home > Information > Melatonin Benefits, Side Effects & Safety Information

Melatonin Benefits, Side Effects & Safety Information

Published: 13th May 2018. Last updated: 21th July 2019.

Shaun Ward MSc ANutr

Staff Writer


Melatonin is a hormone that is responsible for regulating wakefulness, produced mainly within the pineal gland at night in response in darkness.

Melatonin is involved in synchronizing circadian rhythms; biological processes that have a natural 24-hour cycle matched to environmental conditions.

Most importantly, melatonin regulates sleep-wake timing – the natural rhythmic times in which one sleeps and wakes.

As part of normal daily functioning, melatonin synthesis rises in the evening and falls in the morning as darkness seems to stimulate its production, hence why it’s commonly referred to as the “hormone of darkness”.

Once produced, the neurohormone melatonin is released into the bloodstream and can penetrate all body tissues that possess melatonin receptors.

Melatonin’s sleep-promoting actions are predominantly due to its feedback to these receptors, particularly on the suprachiasmatic nucleus – known as the “master clock”. Communication with this nucleus allow melatonin to synchronize the phase and amplitude of the circadian rhythm.

Melatonin As A Supplement

Melatonin is also sold as a dietary supplement, with its use being studied for helping the restoration of the bodies internal clock, and aiding sleeping disorders, such as jet lag, insomnia, or other delayed sleep phase disorders (>3-hour disruption of bodies biological clock).

Recently, the examination of melatonin has seen a dramatic rise, likely due to conclusive evidence that sleeping issues are strongly linked to mental clarity, chronic pain, mental illness, and gastrointestinal disorders. Thus, the need for a natural and safe sleeping remedy is more important than ever.

Sleep disorders affect ~20% of the population, defined by whenever a lower quality of sleep leads to impaired functioning or excessive sleepiness. These sleeping problems usually stem from the side effects associated with obesity, diabetes, and hypertension.

In fact, melatonin has now become one of the most frequently requested non-prescription sleep aids.

Melatonin is readily available to buy without a prescription from many pharmacies, supermarkets, supplement stores and online retailers in the United States. It is prescription-only within the UK and most parts of Europe.

The Potential Benefits of Melatonin

Below is a list of the possible benefits we’ve found:

It May Reduces The Time It Takes To Fall Asleep

Melatonin reduces the time it takes for individuals with delayed sleep phase syndrome (a delay in regular sleeping patterns by >2 hours) to fall asleep, while working to reset the body’s natural sleep-wake cycle [1]

Results vary, however melatonin use seems to reduce sleep onset latency – time to transition from full wakefulness to sleep – by 10-30 minutes in most cases.

It May Improve Sleep Quality

Sleep quality is poorly defined, although it is generally associated with the extent of tiredness and energization upon waking and throughout the day, along with the number of awakenings experienced during the night.

Many studies have demonstrated that melatonin supplementation is able to significantly improve sleep quality. The increased sleep quality has been proven in both measurement-based (via biological analysis) and sensory-based (subjective user experience) trials [2].

Melatonin supplementation has also shown to further improve sleep quality even in the presence of prescription sleeping pills [3].

These findings are especially important when considering that sleep quality is more important than sleep quantity when discussing the impairment of daytime functioning (memory, vigilance, psychomotor skills).

Further, insufficient sleep quality and subsequent mental dysfunction during the day are one of few accurate predictors for quality of life. 

It May Help Alleviate Jet-Lag

Jet-lag occurs when individuals cross several time zones and is a result of the body's internal rhythms being suddenly disrupted by an altered day-night cycle at the destination.

As melatonin is able to regulate the circadian rhythm and sleep-wake timing, it has been proposed as a solution to re-align individuals to their new environment.

Studies conclude that melatonin taken close to the target bedtime at the destination appear to decrease signs of jet-lag when crossing multiple time zones [4].

Dependent on the severity of previously experienced jet-lag, as well as the type of journey being travelled, melatonin can have either a reductive or preventative role in alleviating symptoms.

The benefit is speculated to be greater the more time zones that are crossed, as well as for eastward flights that force the body to adapt to less hours in a given day.

Please note that the timing of melatonin ingestion is critical, as jet-lag can potentially cause a delayed adaptation to destination time if the supplement is taken too early in the day.

It May Help Those With Insomnia

Insomnia is a sleep disorder that is characterized by difficulty falling and/or staying asleep, usually caused from anxiety, stress or depression.

In patients suffering from insomnia, melatonin supplementation has improved sleep maintenance, sleep quality, sleep duration, and number of awakenings [5].

To add to this, several researchers have supported the use of melatonin therapy for the treatment of non–circadian-based insomnia; related to psychological issues as opposed to sleep-wake irregularities [6].

The mechanisms behind this finding are unknown, however they are hypothesized to be due to melatonin’s effect on regulating core body temperature, acting as a muscle relaxant, along with the potential for mild anti-depressant effects. 

How To Use Melatonin

Although dietary melatonin is available through food, the quantities are not adequate enough to induce any noticeable effect on altering the circadian rhythm or sleep quality. Therefore, the most common methods of taking melatonin is through a dietary supplement, typically in capsule/tablet form.

The recommended dosage for melatonin is an extensive topic that has recently led to much debate. However, based on the current scientific literature, there is no evidence that any dosage above 300mcg (0.3mg) is superior to 300mcg in terms of reducing time until sleep, or improving sleep quality [7][8].

In fact, higher dosages tend to either produce the same or inferior results, and lead to an increased likelihood of noticing side effects from its consumption. This is likely due to 300mcg most closely resembling the level of your body’s natural melatonin production at night.

Higher intakes may only cause an excessive and prolonged rise in plasma melatonin concentrations that counteracts any intended reason for its use.

Melatonin is best taken in the immediate period before an individual’s ideal sleeping time (<30 minutes), provided the aim of its use is to help with getting to sleep.

If the goal is to prevent or adjust to jet lag, then as previously mentioned, consumption should be at the time of an ideal sleeping hour at the travelled destination.

Melatonin Safety & Side Effect Information

Melatonin appears to be safe when used short-term, but the lack of long-term studies means that safety cannot be guaranteed for extended use.

Unlike other sleep medications, consumers are unlikely to feel dependent on its use, have a diminished response from repeated use, or experience a withdrawal effect when consumption is stopped [2].

However, there is some caution in advising children and pregnant women to take melatonin due to its potential effects on other hormones.

The potential side effects may be:

  • Headache
  • Dizziness
  • nausea
  • drowsiness
  • abdominal pain
  • constipation
  • fatigue (tiredness)
  • pruritus (itching)
  • hypothermia (severe coldness)
  • tachycardia (fast heart rate)
  • mild depression symptoms
  • morning lethargy
  • skin rashes.

In addition, melatonin supplements can interact with various medications, including:

  • Anticoagulants and anti-platelet drugs
  • Anticonvulsants
  • Contraceptive drugs
  • Diabetes medications
  • Medications that suppress the immune system (immunosuppressants)

If you're considering taking melatonin supplements, check with your doctor first - especially if you have any health conditions.


Melatonin is a hormone that is responsible for regulating wakefulness.

Melatonin is available as a supplement, and taking it 30 minutes before bed, or the ideal sleeping time at a travelling destination, can improve sleep quality and reduce the time it takes to sleep.

Melatonin may also help with preventing and treating jet lag, as well as those who suffer from insomnia.

300mcg (0.3mg) seems to be the best dose for melatonin supplement to get the beneficial effects without potential side effects.

Melatonin is generally a safe supplement, especially compared to other sleep medications, with mild side effects at high intakes.

To Top