What is melatonin?
Melatonin is often called "the sleep hormone" because your brain produces it when it gets dark, signaling to your body that it's time for sleep. It is produced naturally in the pineal gland in your brain from the conversion of the amino acid tryptophan.  It can also be taken in supplement form (often synthesized), and it occurs naturally in some foods like tart cherries and a variety of rice.
Melatonin is not a sedative, so melatonin itself won't knock you out. Instead, it works together with your body's biological clock, also known as the circadian rhythm, to prepare your body for sleep. Scientific research shows that melatonin may help to strengthen and improve sleep-wake cycles, making it possible to adhere to more healthful sleep patterns and making it easier to sleep on a regular schedule. In this article, you'll learn how to use a melatonin supplement for better sleep. 
What affects melatonin production?
Since melatonin production increases when it's dark and decreases when it's light, it's important to create a dark environment for yourself at bedtime.  Exposure to light at night can disrupt your body's production of melatonin.  This is why people who use electronic devices like phones and TVs that generate high-intensity blue light late at night often have trouble falling asleep. Their brains misinterpret this light as daytime and they do not produce enough melatonin to initiate sleep.
Melatonin is also used to counter the effects of jet lag, or an unusual work schedule or someone who suffers from a circadian rhythm disorder. [5,6]
Melatonin levels decrease as you age, with a steady decline after age thirty, which may make it harder to fall asleep as you get older, even if you've never had sleep problems in the past. 
Does melatonin work?
The examples above are just a few factors that affect melatonin production. Melatonin supplementation can be very helpful, allowing people to fall asleep easier in a safer, more natural way compared to prescription sleeping pills.  Melatonin taken orally as a supplement does work since the body recognizes it just like the melatonin it produces naturally.
The benefits of melatonin are often misunderstood. Although studies have shown that some people report significantly better quality of sleep using a melatonin supplement, the majority of evidence shows melatonin's main benefit is to help you get to sleep, not improve sleep quality. [9,10,11]
This means melatonin helps you reach the first stage of human sleep, called NREM-1. It is not the best supplement to help you lower your body temperature (NREM-2 Sleep Stage), get deep sleep (NREM-3 Sleep Stage), or reach REM Sleep (REM Sleep Stage). In this case, there are other nutrients you can take, and lifestyle changes you can make to help you with improving the overall quality of your sleep and support all four stages of sleep.
The melatonin cycle
Your brain typically starts producing melatonin a few hours after dusk (due to darkness), and production peaks at around 4 am, then drops as the dawn approaches to almost nothing by early to mid-morning (due to light levels rising).
When to take melatonin?
Millions of people have difficulty falling asleep at night, and melatonin can be a good solution. Melatonin is often taken about 60 minutes before bedtime to help the transition to sleep mode.
Is melatonin safe?
Melatonin is safe for long-term use when taken orally. Patients often ask me, "Is melatonin addicting?" and I tell them that's it's not, and in fact, it is much safer than sleep medications precisely because it is not addictive. Additionally, you are not likely to experience less of an effect after repeated use, otherwise known as habituation.  My patients also ask, "Can I use melatonin daily?" and the answer is yes, as long as it's taken at the appropriate dose and time of day.
Although melatonin is considered safe and there are no known cases of a melatonin overdose, you should be aware of possible melatonin interactions with medications, especially blood thinners and antidepressants.
How much melatonin should I take to sleep?
Studies show that a standard melatonin dosage for adults is between 0.20 mg and 5 mg, taken 60 minutes before bedtime. It is recommended to start with a smaller dose and work your way upward if needed (at 0.20 mg increments each time you take it). The increasing dosage approach is recommended because taking too much melatonin has the potential to disrupt your sleep cycle rather than balancing it.
Children should have a smaller melatonin dose; reference a melatonin dosing chart based on age and weight. It's recommended to speak with your child's pediatrician prior to use.
Melatonin side effects
Melatonin can cause mild side effects such as short-term feelings of depression, headache, daytime sleepiness, stomach cramps, dizziness, and irritability. Since melatonin can cause drowsiness, don't drive or use heavy machinery within five hours of use.
Melatonin supplements can be found with doses ranging from 0.2 mg to as high as 10 mg. It's important to start at the smaller end of this range. Most people will not need to take more than 1 mg to experience melatonin benefits.
You should also be wary of the quality of melatonin supplements you buy. Tests of melatonin supplements in the US found that the actual content of melatonin contained inside ranged from 83% less than the label claim to 478% more than the label claim.  Since the US FDA does not commonly regulate dietary supplements, this problem is likely to persist, so make sure you choose a reputable melatonin brand.
Is there such a thing as natural melatonin?
Yes, melatonin can be found from natural sources. For example, there are plant-based melatonin sources from a variety of rice and tart cherries. However, there is no evidence of these low-dose natural sources being any more or less effective than the standard synthesized sources.
What are the best melatonin supplements?
Whatever type of melatonin you choose, remember to start small and avoid melatonin pills, as they have a lower absorption rate than liquids. For the best results, seek out a liquid melatonin supplement whenever possible. There are time-release melatonin forms available, but if not taken at the right time of day, it may cause drowsiness that persists and disruption to normal circadian rhythms.
Additionally, if you're taking it for sleep, consider taking other nutrients that support the entire human sleep cycle to get better quality sleep in addition to falling asleep faster. The only supplement that has liquid melatonin and is formulated to support all four stages of human sleep is called REM Sleep by Healthycell.
Synergistic nutrients to take with melatonin for better sleep
Combinations of nutrients that are scientifically proven to help you sleep may be more effective than any single sleep-boosting ingredients alone.
I've tried just about all of these sleep aid formulas, and the best melatonin brand is one that combines liquid melatonin (in the recommended dose) and the key nutrients that support the 4-stages of sleep. My highest recommendation is REM Sleep by Healthycell.
Expertly formulated by physicians and nutritionists, REM Sleep is a blend of drug-free, non-habit-forming ingredients that supports all four stages of human sleep: NREM-1, NREM-2, NREM-3 (Delta Brainwave Deep Sleep), and REM.†
REM Sleep comes in a single-serve, recyclable liquid gel pack. It's also the only sleep supplement made with MICROGEL™ technology to ensure maximum (and timely) absorption of the premium sleep supporting nutrients. It includes premium ingredients like valerian, lemon balm, magnesium, L-theanine, melatonin, 5HTP, and GABA, to help you fall asleep, stay asleep throughout the night, sleep deep, and achieve restorative REM sleep, so you can wake up refreshed.†
To your health,
Dr. Vincent Giampapa, MD, FACS
Visiting Scholar, The Sinclair Lab
Harvard University, Boston, MA
Cell Aging Researcher & Author
Director, Cell Health Institute