Quick Answer: Yes, 40mg of melatonin is considered an extremely high dose and is not recommended for sleep. The physiological dose is 0.3mg. Taking 40mg (130 times the natural amount) can cause severe side effects including nausea, dizziness, hormone disruption, and "melatonin resistance" where the supplement stops working entirely.
Brad, Owner since 1987: "We have been helping Brantford families sleep better since 1987. Every customer gets personal attention, honest advice, and the kind of follow-up service you just do not get from big box stores."
Reading Time: 4 minutes
You started at 5mg. It stopped working. You went to 10mg. Then 20mg. Now you are taking four pills (40mg) just to feel drowsy.
At Mattress Miracle, we hear this story of escalation often. Customers believe they are "immune" to melatonin. They aren't immune; they are saturated.
Taking 40mg of a hormone is not a sleep strategy; it is a chemical sledgehammer that often breaks the very system you are trying to fix.
130x The Natural Level
Your brain produces about 0.3mg of melatonin per night. That is a tiny, precise signal.
The Math:
40mg ÷ 0.3mg = 133 times the natural dose.
Imagine if you took 133 Tylenols instead of 1. Or drank 133 cups of coffee. While melatonin is less toxic than those drugs, flooding your brain with that much hormone causes your receptors to "shut down" to protect themselves. This is why it stops working.
Physical Symptoms of Overdose
At 40mg, you are likely experiencing toxicity symptoms, even if you don't realize they are from the pills:
- Hypothermia: Melatonin lowers body temperature. You might feel freezing cold at night.
- Gastric Distress: Nausea, stomach cramps, and diarrhea are common at high doses.
- Mental Fog: Severe grogginess that lasts until the afternoon because your liver can't clear the huge dose fast enough.
- Anxiety/Jitters: Paradoxically, high doses can trigger adrenaline, making you feel anxious instead of sleepy.
The Hormone Crash
Melatonin interacts with other hormones, including cortisol and reproductive hormones (LH/FSH). Chronic mega-dosing (40mg+) can potentially disrupt your menstrual cycle (in women) or testosterone levels (in men), though more research is needed.
More importantly, it suppresses your body's own production. Your pineal gland stops making melatonin because you are providing so much externally. If you stop taking it, you will have zero natural melatonin, leading to severe rebound insomnia.
How to Fix Your Tolerance
If you are taking 40mg, you need a "Melatonin Detox."
- Stop Cold Turkey? No. Taper down. Go to 20mg for three days. Then 10mg. Then 5mg.
- The "Washout" Period: Once you taper down, take a week off completely. Your sleep will be bad. Expect it. You need to clear the receptors.
- Restart Tiny: When you restart, take 0.5mg or 1mg. You will be shocked that a tiny dose works better than the mega-dose because your receptors are sensitive again.
The Mechanical Alternative
If you needed 40mg to sleep, your problem likely isn't hormonal - it's physical. Pain overrides melatonin. If your mattress is causing back pain, no amount of hormone will keep you asleep. Fix the bed (e.g., a Restonic Hybrid) and you won't need the mega-dose.
8 min read
Frequently Asked Questions
Shop: Adjustable Beds at Mattress Miracle
Shop This Topic at Mattress Miracle
Popular picks at Mattress Miracle:
Or browse all mattresses in our Brantford showroom.
Find Your Perfect Mattress at Mattress Miracle
We are a family-owned mattress store in Brantford, helping our community sleep better since 1987. Come try mattresses in person and get honest, no-pressure advice.
441 1/2 West Street, Brantford, Ontario
Call 519-770-0001Is 40mg ever prescribed?
Only in very specific medical cases, such as part of cancer treatment protocols or for severe neurological disorders, and always under strict doctor supervision. Never for simple insomnia.
Will 40mg kill me?
Unlikely to be fatal, but you might wish it were. The headache, nausea, and vertigo can be debilitating. If you took it by accident, have someone watch you and stay hydrated.
Why do they sell high doses?
Because supplements are unregulated. Companies know consumers think "More = Better." Selling a 10mg pill that you have to take 4 of makes them more money than selling a 1mg pill that works.
Does magnesium help with the detox?
Yes. While you taper off melatonin, take Magnesium Glycinate. It relaxes the body physically without affecting the melatonin receptors, helping you bridge the gap.
Visit Our Brantford Showroom
Mattress Miracle
441 1/2 West Street, Brantford
Phone: (519) 770-0001
Hours: Mon-Wed 10-6, Thu-Fri 10-7, Sat 10-5, Sun 12-4
Our team has 38 years of experience helping customers find the right sleep solution. Call ahead or walk in any day of the week.
Visit Our Brantford Showroom
We are located at 441½ West Street in downtown Brantford. Free parking available. Our team does not work on commission, so you get honest advice based on your needs.
Mattress Miracle , 441½ West Street, Brantford, ON · (519) 770-0001
Hours: Monday–Wednesday 10am–6pm, Thursday–Friday 10am–7pm, Saturday 10am–5pm, Sunday 12pm–4pm.
Sources
- Andersen, L. P. H. et al. (2016). "The Safety of Melatonin in Humans." Clinical Drug Investigation, 36(3), 169-175. PubMed 26692007. Reviews melatonin safety and upper tolerable doses in adults.
- Besag, F. M. C. et al. (2019). "Adverse events associated with melatonin for the treatment of primary or secondary sleep disorders: A systematic review." CNS Drugs, 33(12), 1167-1186. PubMed 31722088. Documents side effects at higher doses including next-day grogginess and nightmares.
- Health Canada. (2024). Melatonin: Natural Health Product Monograph. canada.ca