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Melatonin Side Effects: What You Need to Know

| Modified on Nov 10, 2025
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Melatonin Side Effects

Melatonin is a popular supplement millions use to improve sleep quality and combat insomnia. While generally considered safe, it's important to be aware of potential melatonin side effects to make an informed decision about its use. This article covers the key side effects, providing a comprehensive guide for those considering melatonin.

Common Side Effects of Melatonin

  1. Drowsiness: The primary function of melatonin is to regulate sleep-wake cycles, so drowsiness is a common effect. It's advised to take melatonin 30 minutes to an hour before bedtime to avoid feeling sleepy during the day.

  2. Headaches: Some users report mild to moderate headaches after taking melatonin. This could be due to the body adjusting to the supplement or a sensitivity to its ingredients.

  3. Dizziness: A feeling of dizziness or lightheadedness can occur, especially when getting up quickly. To minimize this effect, rise slowly from a sitting or lying position.

  4. Nausea: Melatonin can cause stomach discomfort or nausea in some individuals. Taking the supplement with food may help reduce this side effect.

  5. Vivid Dreams or Nightmares: Some users experience changes in dream patterns, leading to more vivid dreams or nightmares. If this becomes troublesome, consider reducing the dosage.

Less Common but Notable Side Effects

  1. Mood Changes: Melatonin may affect mood, leading to feelings of depression or anxiety in some users. If you notice significant mood changes, it's important to consult a healthcare professional.

  2. Hormonal Effects: Since melatonin is a hormone, it can impact other hormonal processes in the body. Women may experience changes in menstrual cycles or breast milk production.

  3. Daytime Sleepiness: While melatonin helps with nighttime sleep, some users may feel excessively sleepy during the day. Adjusting the timing or dosage can often mitigate this effect.

  4. Interaction with Medications: Melatonin can interact with various medications, including blood thinners, immune suppressants, diabetes medications, and contraceptives. Always consult with a healthcare provider before starting melatonin if you are on other medications.

Who Should Avoid Melatonin?

  • Pregnant or Breastfeeding Women: Due to limited research on its safety in these groups, it's recommended to avoid melatonin unless advised by a healthcare provider.
  • Individuals with Autoimmune Disorders: Melatonin can stimulate the immune system, potentially exacerbating autoimmune conditions.
  • Children and Adolescents: Melatonin can affect hormonal development, so it's best used under medical supervision in younger populations.

Tips for Safe Melatonin Use

  • Start with a Low Dose: Begin with the lowest possible dose to see how your body reacts. Common starting doses range from 0.5 mg to 1 mg.
  • Time It Right: Take melatonin 30 minutes to an hour before your intended sleep time.
  • Monitor Your Body’s Response: Keep track of any side effects and adjust the dosage or timing accordingly.

Conclusion

Melatonin is a helpful supplement for improving sleep, but it's crucial to be aware of potential side effects. You can use melatonin safely and effectively by starting with a low dose, timing it properly, and monitoring your body's response.

Continue reading the comments below to learn how melatonin has caused various side effects in our readers. Let us know if you've ever had melatonin side effects!

Related Links:

Melatonin: More Than Sleep | A Guide to Benefits & Dosing


The comments below reflect the personal experiences and opinions of readers and do not represent medical advice or the views of this website. The information shared has not been evaluated by the FDA and is not intended to diagnose, treat, or prevent any disease or health condition. Always consult a qualified healthcare professional for medical concerns.

7 User Reviews

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Posted by R B (Somewhere in Europe) on 11/08/2025 93 posts

According to a preliminary study, long-term use of melatonin supplements is associated with a higher risk of heart failure diagnosis, heart failure hospitalization and death from any cause in chronic insomnia.

Source: https://newsroom.heart.org/news/long-term-use-of-melatonin-supplements-to-support-sleep-may-have-negative-health-effects

I hope this will help.

Replied by Art
(California)
11/09/2025
2747 posts

Hi RB,

I recently replied to this study on another forum, and here is what I had to say :

To start, you have to consider the population they are dealing with, insomniacs.

People with insomnia are already at significantly increased risk for heart failure regardless of age, sex or weight differences and the risk increases with the number of insomnia symptoms. The dose of melatonin used for the purpose of sleep is likely too low and too short lived in the body to provide the heart protective effects that studies have already suggested that melatonin may offer.

If a person is taking melatonin for insomnia, the problem is likely already significant suggesting that they are already and have probably been having insomnia symptoms for sometime. There is a reason why they said this statement :

' The association between melatonin and increased risk of heart failure or death found in this study, which cannot prove a cause-and-effect relationship, raises safety concerns about the use of melatonin, which is widely available, and may warrant more research on melatonin to assess its cardiovascular safety, researchers said. ' The underlined part of this statement pretty much says it all regarding this research, it didn't prove anything!

They can't prove cause and effect for the simple reason that the underlying disease, INSOMNIA, already significantly increases the risk of heart failure and many other health issues.

Now let's look at another statement from article :

' A review of 5 years of health records for more than 130, 000 adults with insomnia who had used melatonin for at least a year found they were more likely to be diagnosed with heart failure, require hospitalization for the condition or die from any cause. '

If you take out the words, " used melatonin " and replace them with the word "insomnia" The statement is not only true , but is already scientifically proven, but this article seems to leave that hugely important detail out of these highlights!

This seems like saying that ambulances are almost always at serious auto collision sites, so does that mean they are the cause of the accident?

This research was not peer reviewed and imo, it may not make it through that process with success.

Another point they mentioned is that the patients reviewed in their research had to have taken melatonin long term, as in one year or more of melatonin intake in order to be accepted into the study and were compared to people with insomnia who didn't show in their records that they were taking melatonin or any medications for insomnia. They also excluded people from the study who already had heart failure.

First, if you have insomnia and you are not taking a prescription sleep medication or melatonin, that suggests your insomnia may not be that bad or advanced.

Second, if you are not taking a prescription sleep medication, but you are taking melatonin, that might suggest that your insomnia is worse than those who are essentially taking nothing for their insomnia. The worse the insomnia the greater the chance for heart failure. I didn't see any mention of how long the non melatonin group had had insomnia, but that would be a very highly relevant point as the longer you have had insomnia the greater the risk for heart failure and many other health issues. In order to be in the melatonin group, you had have been taking melatonin for at least a year or more, suggesting that the melatonin group had had insomnia for at least a year or longer. There is no indication of length of time with insomnia for the non melatonin group. It seems realistic to think that a person who has had insomnia for three months might fair better than a person who has had insomnia for at least a year and the science confirms this because the longer you have had insomnia the greater your chance for heart failure.

Had they allowed people to be included who were using prescription medications for insomnia, I think the title for the article would have looked much different.

Lastly, there are no other melatonin studies that I have ever seen to support the idea that longer term use of melatonin causes or contributes to heart failure, but there are real studies to suggest that melatonin may have heart protective effects such as this :

https://pmc.ncbi.nlm.nih.gov/articles/PMC9251346/

Here is a relevant quote from the link :

' Numerous studies have shown that melatonin has significant functions in cardiovascular disease, and may have anti-aging properties. The ability of melatonin to decrease primary hypertension needs to be more extensively evaluated. Melatonin has shown significant benefits in reducing cardiac pathology, and preventing the death of cardiac muscle in response to ischemia-reperfusion in rodent species. Moreover, melatonin may also prevent the hypertrophy of the heart muscle under some circumstances, which in turn would lessen the development of heart failure. Several currently used conventional drugs show cardiotoxicity as an adverse effect. Recent rodent studies have shown that melatonin acts as an anti-oxidant and is effective in suppressing heart damage mediated by pharmacologic drugs. Therefore, melatonin has been shown to have cardioprotective activity in multiple animal and human studies. Herein, we summarize the most established benefits of melatonin in the cardiovascular system with a focus on the molecular mechanisms of action.

Trying to pass this off as relevant research, gives good researchers a bad name.

I won't say that this was a hit piece on melatonin, because I understand that some researchers will do research just to get paid, but in my opinion, this research was a terrible waste of research dollars that could have been used for a much better purpose.

Art

Ruralady
(Illinois)
11/10/2025
145 posts

I, especially didn't pay any attention to the report I suspect was put out by Big Pharma. It's not the first time they've done this and won't be the last. It's to protect their massive gravy train since most people aren't buying into their nonsense that they are the ultimate gods when it comes to good health. Natural is the way to go unless you're in a life or death situation.


Side Effects
Posted by Sunshiney (Hotlanta, GA) on 04/28/2025

I am a person that is very sensitive to melatonin. I've read about all the remedies it has the ability to provide over the years. Yet if I take oral melatonin in a dose higher than say 1mg, I run the risk of having horrendous nightmares. I wonder if anyone else has had this experience and if they found a way to overcome it?

I'd love to try this remedy, but the fear of having a really traumatic, horrendous nightmare keeps me away.

That said, I used to be even more sensitive. Previously, it was 300 micrograms (not milligrams) was all I could take. Now if I choose to take it, I can handle 1 milligram. I don't know what in the my body changed, but whatever it is/was, it took years to do it.

Thanks in advance for the help, folks!

Replied by Art
(Califotrnia)
04/28/2025
2747 posts

Hi Sunshiney,

Some people have a hard time taking oral melatonin and for those, it is more effective to get your extra melatonin through multiple natural means. I wrote an article explaining about this here :

https://www.earthclinic.com/supplements/how-to-increase-melatonin-naturally.html

There are many foods that contain melatonin and previously I thought that the amounts available through these foods was too small to have any benefit, but newer studies are suggesting that even these small amounts can be very beneficial. Here is a link to the most comprehensive list of foods that contain melatonin as well as how much melatonin they contain that I have been able to find to date. Once you go to the link, you will have to scroll down to Table 1 :

https://pmc.ncbi.nlm.nih.gov/articles/PMC5409706/

Another potential option is to test melatonin lotion (ML) or melatonin gel (MG) as I have not had any feedback on these two causing vivid dreams. Here are two links that describe how to make each one :

ML :

https://www.earthclinic.com/supplements/melatonin-lotion.html

MG:

https://www.earthclinic.com/supplements/melatonin-gel.html

Art


Side Effects
Posted by Bindi (New Jersey) on 08/06/2024

HI Art,

I've tried melatonin a couple of times. Each time the side effects were terrible: nightmares, unable to breathe as I struggled to wake up, dizziness and nausea. felt I was drowning .the dose was 1.5 mg.

I suffer from Ibs, fibromyalgia, arthritis, anxiety and a lot of stress. Would this have interfered with neurotransmitters/hormones?

Thank you.

Replied by Art
(California)
08/07/2024
2747 posts

Hi Bindi,

If 1.5 mg of melatonin caused you that much distress, then all forms of supplemental melatonin should be off your list of supplements! All is not lost though. Instead, you can get your melatonin from the earlier morning and later afternoon sun exposure, foods rich in melatonin and red light therapy. These natural forms of melatonin seem to avoid any potential side effects of melatonin and the sun can improve your circadian rhythms also.

I wrote an article awhile back that describes a few natural ways to get melatonin here :

https://www.earthclinic.com/supplements/how-to-increase-melatonin-naturally.html

Art


Side Effects
Posted by Deb (Treasure Island, FL) on 07/24/2021

I have noticed nose bleeds with melatonin


Side Effects
Posted by Kenny H (TN) on 03/17/2021

For many years, I had trouble sleeping and took Melatonin and always felt groggy and a hangover from taking it, but since pot is not legal in TN, what choice did I have? And then all of a sudden, my whole system flipped and then suddenly I couldn't get enough sleep! Suddenly 8 hrs was not enough and I always felt exhausted! What a nightmare! Not saying the melatonin had anything to do with it, but it what I was taking and it scared the holy hell out of me!

Now I'm fighting diabetes and liver damage and thyroid malfunction which came on all of a sudden also and while I am overcoming that slowly but surely by alternate day fasting, cutting ALL wheat products out of my diet, and the old timey cottage cheese and oil (Flax, black seed & Hemp oil) medicine cancer cure remedy!

But I'm not my old self by any stretch as before I started taking melatonin every night and so am very leery about ever taking melatonin again! Besides it always makes you feel so tired and groggy and who the hell needs that when your 65 yrs old? Certainly not me! So the jury is still out on that one! The side effect of melatonin is it makes you drowsy and tired, and I need just the opposite of that!

Replied by Art
(California)
03/17/2021
2747 posts

Hi Kenny,

Yes, there are people who can not tolerate melatonin as I have mentioned many times on EC, but the majority of people do tolerate melatonin as shown in many studies. Generally, as soon as you realize that there is a negative reaction to melatonin or you are not tolerating melatonin because of symptoms such as you described, it is probably a very good idea to stop using melatonin immediately rather than continuing. It is sort of like your body is trying to let you know that this is not compatible with you.

Art

Denise E
(Crescent City, CA)
03/29/2023

I doubt I'd wake up at all if I took as much as some folks do, I am shocked don't mind saying. I took a 10mg tablet and felt groggy for most of the a.m. so please be careful with trying it out.

I need something to help me sleep as I am weaning off clonazapam and melatonin was again suggested. I was having a hard time at night, not upping to my usual dose of 1 mg of clonazapam, so I'd just fall back into the 1 mg per day. I'm hoping just a smaller dose of Melatonin will help me and not leave me hungover, or groggy.

I found some bottles of 5 mg Melatonin, but then I kept looking, and found 3 mg bottles so I bought the later. Very inexpensive and I am hoping. It these don't work for me, then I guess I'll have to find another hopefully safe sleeping supplement.

Art
(California)
03/29/2023
2747 posts

Denise,

Amazon has melatonin down to .3 mg. for some people that is all they need for sleep. I take 132 mg/night, but I had to work my way up otherwise I felt very tired the next morning. Even now, when I move my dose up above 132 mg, I will feel it the next morning.

https://www.amazon.com/Landau-Melty-Melatonin-300-Tablets/dp/B07LDVJXSQ/ref=sr_1_3?crid=2MNKLHN4LMNO3&keywords=melatonin+.3+mg&qid=1680133910&sprefix=melatonin+.3+mg,aps,128&sr=8-3

In one study it showed that just 2 mg of melatonin before bed could reduce nocturia, which is very helpful in getting more restful sleep.

I think if you have not already been taking melatonin for awhile and then just take 10 mg, it will likely make most people feel tired in the morning. Also, not everybody can tolerate melatonin, even at low doses. For those people it is better to use the natural ways to increase your melatonin levels because melatonin made in the body does not cause side effects. I wrote about how to do that here :

https://www.earthclinic.com/supplements/how-to-increase-melatonin-naturally.html

Art

Sam
(Miami)
04/01/2023

Denise, Google Mexidol. Also chinese herbal formulas: bupleurum&dragon bone is one of what it is called “shen tonics” that is very good. Better yet see an acupuncturist/herbalist. Never buy any supplements on Amazon. Mexidol is an exception-you can only buy it on Amazon. It might take up to 3 years to get off clonazepam.


Side Effects
Posted by HisJewel (New York) on 01/31/2021
★★★★★

Regarding Melatonin Side Effects,

Melatonin was a big help in starting my fight to get well even with side effects.

I decided to reorder some more Melatonin, because I was glad that I had it on hand to meet a possible emergency during my coughing fits. As I mentioned I took about 100mgs of Melatonin for each of 3 days. I took 4 to 5 pills a few times a day and once at night. They were 5mgs each. No, my brand did not make me sleep or sleepy; however, I found that when I was ready to sleep they let me sleep at least an hour or two at night. The side effect I had was loose stools.

Some years ago, I had ordered some Melatonin from eBay. I am not sure why I bought them, I do remember reading a book back then that said it was good for stopping any further memory loss in its track. Anyway, this Melatonin product was from overseas, it was a powder, and a very high mgs per tiny scoop. I do not remember the company. I remember going to sleep that night and not waking up until morning. In the garbage it went. As I used to do all night prayer often and too much sleep would interfere with my work. The interesting thing is I do not remember having any side effect, only what it said it would do give me sleep.

The Melatonin that I had on hand when I was sick this month, I bought last year because Earth Clinic, Art and others posted Melatonin benefits for COVID 19.When I decided to buy more, I noticed that I needed to find out what "Other ingredients" are in each brand and kind of Melatonin. The company that I got mine from had at least 3 different kind of Melatonin mixtures. I did not want any artificial sweeter in mine so I was reading the labels. Then it dawn on me that perhaps one of the" Other ingredients" in the brand that I already had was what caused the side effect that I encountered. So please read the label.

HisJewel

Replied by Art
(California)
01/31/2021
2747 posts

Hi HisJewel,

Thank you for the feedback on melatonin!

What I have noticed is that some people can develop diarrhea from HDM [High Dose Melatonin], but in the few people I have seen or heard of this side effect, that delay, can vary from 3 days to 3 weeks. In either case, the delay makes it possible to use melatonin long enough to help achieve the desired result with Covid-19 and it may be possible to use melatonin for a very brief period even if diarrhea does occur in an attempt to have maximal effect on Covid-19. Stoppage of HDM seems to allow a fairly quick recovery from the diarrhea. I still feel that the combination of melatonin plus the addition of the Xlear Nasal Spray, suggest the potential for a quick recovery.

Here is a link to what I wrote about Xlear Nasal Spray and Covid-19 : Https://www.earthclinic.com/xlear-for-covid-recovery.html

Art


Side Effects
Posted by Gertjr (Madison) on 09/16/2020

I've been taking a, for me, high dose of melatonin for insomnia. I've been taking 10 mg at 7, another 10 mg at 8 and one more at 9, then off to bed. The first night I slept fine, next night not so great and, but the third night, was having stomach troubles. So, I backed off for a week. I then to 10 mg at 7 and, at 9, took a 10 mg timed release tablet. I kept waking up but my concern is that I was dizzy. I had to be careful getting up and then was fine. So I stopped it for several days.

Then, last night, I took a 5 mg regular tablet and, during the night, woke up dizzy. Even at the gym this morning, doing barbell bench presses, I was dizzy upon sitting up. So, is this the melatonin or something else? I stay hydrated and my blood pressure was good (I took it several times), so it's not that.

Possibly low blood sugar? I had not eaten for some time when it happened. Any thoughts? I swim, so wonder if it's not my ears? I do not have vertigo during my normal day, only upon rising from flat to sitting (of course I don't stand until it passes). I don't want to visit a dr until I've eliminated other causes. Thanks. I really need relief of the insomnia! I've taking benadryl and want to stop.

Replied by Bbhe
(Nyc)
09/21/2020

I definitely feel your pain. I had insomnia for years. Turned out it was gluten. (Yeah, I thought I'd tried eliminating it, but I guess I hadn't. If I get even a pinch of flour, ping, eyes wide open all night long.) Melatonin makes me loopy as well unless I take a tiny tiny dose. Also, if I do high intensity workouts sometimes that makes it worse, especially if I'm fasted.

GOOD LUCK and SWEET DREAMS.


Side Effects
Posted by Manti (Tulsa, OK) on 07/31/2009

I was wondering about the use of melatonin..some use it as a sleep aid and i've heard it works really well..is there any other uses..are there any side effects of the oral form, is there any longterm side effects noted from using it?

Replied by Stacey
(Greensboro, Nc)
08/04/2009

Hi Manti,

I use to take melatonin, but stopped because of two side effects. One side effect was that it acted as a diuretic, so I really didn't get much sleep b/c of running to the bathroom. The other was very real dreams. It got to the point that I could not figure out if I had really had conversations with people in my dreams versus reality. Melatonin is actually a hallucinagen your body naturally produces. I guess when you add more of the chemical to your body, it coases you to dream more realistically.