For most adults, 5mg of melatonin is more than enough. It’s actually several times higher than what sleep specialists typically recommend as a starting dose, and it far exceeds what your body produces naturally. While 5mg won’t cause serious harm for most healthy adults, a lower dose is likely to work just as well, with fewer side effects like morning grogginess.
How 5mg Compares to What Your Body Makes
Your brain’s pineal gland produces melatonin every evening as light fades, signaling to your body that it’s time to sleep. The amount it releases is tiny: roughly 0.1mg to 0.5mg. A 5mg supplement delivers 10 to 50 times that amount in a single dose. This doesn’t make it dangerous, but it does mean your body is processing far more melatonin than it was designed to handle, which can lead to side effects and may not improve your sleep any more than a smaller dose would.
What Doctors Actually Recommend
Clinical guidelines tend to start well below 5mg. The NHS recommends 2mg slow-release tablets for both short-term and longer-term insomnia in adults. For jet lag, a 3mg standard tablet is the usual recommendation. The CDC goes even lower for circadian rhythm shifts like jet lag, noting that 0.5 to 1mg is often sufficient to produce a meaningful shift in your sleep-wake cycle. The CDC specifically advises against doses above 5mg for jet lag because excess melatonin can linger in your system and end up active at the wrong time of day as your body breaks it down.
The pattern across guidelines is consistent: effective doses start at 0.5mg and rarely need to exceed 3mg. The 5mg tablets that dominate store shelves reflect market trends more than medical evidence. Many people assume a higher dose means stronger effects, but melatonin doesn’t work like a conventional sleep aid where more equals more sedation. It’s a timing signal, not a sedative, and flooding your receptors with excess melatonin doesn’t sharpen that signal.
Does More Melatonin Help You Fall Asleep Faster?
Melatonin does reduce the time it takes to fall asleep, but the effect is modest regardless of dose. A meta-analysis published in eClinicalMedicine found that melatonin shortened the time to fall asleep by about 15 minutes compared to placebo. That’s meaningful if you’re lying awake for an hour, but it’s not the dramatic knockout effect many people expect. And critically, studies consistently show that very low doses (0.3 to 1mg) produce similar results to higher ones. The 5mg dose isn’t buying you much extra benefit over 1 or 2mg for most people.
Side Effects at Higher Doses
The most common side effects of melatonin include headache, dizziness, nausea, and daytime drowsiness. Vivid dreams or nightmares are less common but well documented. These side effects tend to be more pronounced at higher doses because more melatonin stays in your bloodstream longer, sometimes well into the next morning. If you’re waking up groggy or foggy after taking 5mg, the dose is likely too high for you.
This is especially relevant for older adults. After taking melatonin, older adults reach higher peak blood levels and clear the hormone more slowly than younger people. A systematic review in Drugs & Aging found that higher doses in older adults produced prolonged elevation of melatonin levels into the following day, potentially disrupting the very sleep-wake cycle the supplement was meant to fix. The review recommended that older adults use the lowest possible dose of immediate-release melatonin to avoid these supra-physiological levels.
The Label Might Not Match the Pill
There’s another wrinkle worth knowing about. Because melatonin is sold as a dietary supplement in the United States, it isn’t held to the same manufacturing standards as prescription medications. A study highlighted by the American Academy of Sleep Medicine found that more than 71% of melatonin supplements tested did not contain within 10% of the amount listed on the label. The actual melatonin content ranged from 83% less to 478% more than what the bottle claimed. Lot-to-lot variability within a single product varied by as much as 465%.
That means your 5mg tablet might contain anywhere from less than 1mg to over 25mg. The study also found serotonin, a completely different and more tightly regulated substance, in 26% of tested supplements. If you’re taking 5mg and not noticing any effect, inconsistent dosing from the manufacturer could be a factor. Choosing a product that has been independently tested by a third-party lab (look for USP or NSF certification on the label) can reduce this uncertainty.
Dosing for Children and Teens
If you’re asking about 5mg for a child, the answer depends on age. Melatonin is not recommended at all for children under 5. For children aged 5 to 12, the recommended range is 1 to 3mg. Teens should not exceed 5mg, making it the absolute upper limit rather than a starting point. Exceeding recommended doses in children can cause daytime grogginess, and more serious effects like diarrhea, vomiting, confusion, short-term depression, and an increased risk of seizures have been reported. Starting with the lowest effective dose is particularly important for younger users.
How to Find Your Right Dose
If you’re currently taking 5mg and sleeping well without morning grogginess, there’s no urgent reason to change. But if you’re experiencing side effects, or if you’re just starting melatonin, beginning at 0.5 to 1mg is a smarter approach. Take it 30 minutes to two hours before your intended bedtime. Give each dose at least a week before deciding it isn’t working, since the effects on your circadian rhythm can take several days to stabilize.
If 1mg doesn’t help after a week, you can move up to 2 or 3mg. Most people find their effective dose well below 5mg. If you’re already at 5mg and still struggling to fall asleep, taking more is unlikely to help. Persistent insomnia that doesn’t respond to melatonin usually has other causes, whether it’s anxiety, poor sleep habits, light exposure before bed, or an underlying sleep disorder that melatonin can’t address.