Melatonin sits in the supplement aisle of every pharmacy in Australia, marketed as a quick fix for poor sleep. The reality is more specific. Melatonin is a hormone your body produces naturally, not a sedative, and the gap between what it does and what most people assume it does is surprisingly wide. Understanding that gap is the difference between using it well and wasting your time.
What melatonin actually is
Melatonin is a hormone produced by the pineal gland, a small structure deep inside the brain. The pineal gland releases melatonin in response to darkness. It rises in the evening, peaks somewhere between 2 am and 4 am, and drops off as morning light hits your eyes. The hormone doesn't knock you out. It signals to your brain and body that it's dark and time to prepare for sleep, which is a very different mechanism from a sleeping pill.
The production of melatonin is tightly linked to your circadian rhythm, the internal 24-hour clock that governs nearly every biological process in your body. When your circadian rhythm is running on schedule, your melatonin levels rise at the right time and sleep follows naturally. When it's disrupted, melatonin timing shifts and sleep falls apart with it.
When taking melatonin makes sense
Supplemental melatonin works best when the goal is to shift your body clock forward or back, not simply to increase how sleepy you feel. Three situations genuinely suit it.
- Jet lag. Flying across time zones pushes your melatonin cycle out of sync with local time. Taking a low-dose supplement at the destination's bedtime for two to three nights can help the clock reset faster.
- Shift work. People rotating between day and night shifts have chronically misaligned melatonin rhythms. Timed supplementation can help anchor a new sleep window.
- Delayed sleep phase disorder. Some people naturally produce melatonin very late, making early bedtimes feel impossible. A small dose taken three to four hours before the desired sleep time can shift the rhythm earlier over several weeks.
For plain insomnia, meaning difficulty sleeping despite normal timing, evidence for melatonin is weaker. A 2022 meta-analysis published in the journal PLOS Medicine found melatonin reduced the time to fall asleep by roughly seven minutes in adults with primary insomnia. Clinically useful? Possibly. A cure? No.
How much to take and when timing matters
Most Australian pharmacies stock 1 mg, 3 mg, and 5 mg tablets. The common mistake is reaching for the highest dose. Research consistently shows that 0.5 mg to 1 mg is as effective as 5 mg for resetting the circadian clock, and larger doses can cause grogginess the next morning rather than better sleep the night before.
Timing is more important than dose. For jet lag, take melatonin at your destination's local bedtime. For a standard sleep-onset delay, take it 30 to 60 minutes before your desired sleep time, not at your usual bedtime. If your usual bedtime is the problem, taking melatonin at the same time achieves nothing.
Light exposure matters too. Taking melatonin and then scrolling your phone for an hour sends competing signals to the pineal gland. Bright light, particularly blue-spectrum light from screens, suppresses melatonin production regardless of whether you've taken a supplement. This connects directly to the logic of sleep hygiene: the habits and environment around sleep shape the hormone's effectiveness as much as the supplement itself does.
Is melatonin safe in Australia?
In Australia, melatonin above 0.5 mg is a prescription medicine for adults. The Therapeutic Goods Administration (TGA) classifies melatonin products above 0.5 mg as Schedule 4 (prescription only) for anyone under 55 years old. Adults 55 and over can access 2 mg slow-release melatonin over the counter under the brand name Circadin, specifically for short-term insomnia. Anyone else wanting a higher dose needs a GP script.
Short-term use at low doses is considered safe for most adults. Side effects are generally mild: next-day drowsiness, headache, and dizziness are the most reported. There's no strong evidence that melatonin supplementation suppresses the body's own production over time, though this remains a point of ongoing research. For children and adolescents, melatonin is only appropriate under medical supervision.
What melatonin won't fix
Melatonin won't address the most common causes of poor sleep in Australia. Stress and anxiety are not circadian rhythm problems. Neither is sleep apnoea, which affects roughly 5% of Australians and physically interrupts breathing during sleep. Pain, caffeine, alcohol, and inconsistent sleep schedules all impair sleep through mechanisms melatonin can't touch.
Cognitive behavioural therapy for insomnia (CBT-I) has a far stronger evidence base for chronic insomnia than any supplement. It works by restructuring the thoughts and behaviours that sustain sleeplessness, and its effects last long after the program ends. If poor sleep is a persistent problem rather than a short-term disruption from travel or shift work, CBT-I is worth pursuing through a GP referral before reaching for any supplement.
Melatonin is a useful, well-tolerated tool for a specific set of problems. Used correctly and at the right dose, it genuinely helps. Used as a general sleep aid for someone with unaddressed anxiety or a chaotic schedule, it mostly fills a gap that isn't there.