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Side Effects Of Melatonin: 8 Groups Should Avoid Taking Melatonin

Melatonin, also known as the ‘hormone of darkness’ is a hormone responsible for the regulation of your sleep-wake cycle. However, promoting and regulating sleep is only one of its physiological functions.

This hormone plays an important role in bodily functions, the functions of organs like the kidney or liver, and helps regulate blood pressure and cardiovascular issues. Melatonin is also shown useful in cases of tumors and cancers, where it prevents oxidative stress to promote the growth of cancerous cells.

Now, all of this sounds rather impressive, and sure enough, because melatonin is a naturally produced hormone coming from the very brain, no one would suspect it harmful. However, melatonin supplements, on the other hand, are raising some eyebrows in the medical community.

Over the past few years, melatonin supplements have been studied concerning their possible side effects. Turns out, melatonin intake can cause a dozen of adverse effects, which can pose a long-term danger. In the following paragraphs, we’ll take a look at the major side effects, every melatonin producing company would hide from you. So, let’s get started!

Adverse Effects Of Melatonin Intake: Overview

Adverse Effects Of Melatonin Intake Overview

Image Source: Terry Cralle, RN

Consumption of food supplements that contain melatonin or mainly contain melatonin has shown adverse effects in numerous studies. The most frequently reported side effects include; headaches, dizziness, drowsiness, tremors, migraine, nausea, vomiting, abdominal pain, nightmares, vivid dreams, and irritability. There were even cases of supplement abuse for suicide attempts through melatonin overdose.

The reason for such adverse effects was traced to an incorrect presentation of the amount of melatonin a bottle of supplements truly contains. Investigation shows that melatonin supplement bottles can have 4 times more melatonin than indicated. This can affect one’s health significantly, because of the higher the dose, the serious and more frequent side effects.

However, this is not the only reason side effects occur. Sometimes, doctors do NOT prescribe a suitable dosage, or the patients decide to dose themselves as they want. Some people even tend to drink alcohol with melatonin, hoping to emphasize the sedative effects. But, they just cause even more serious side effects.

Melatonin Side Effects

  • Headaches and migraines – One study showed that melatonin intake in doses between 0.5 and 10mg caused the participants to experience headaches and migraines as possible side effects of long-term intake. Other studies also showed headaches and migraine attacks as the most frequent side effects, while some participants also experienced nausea, dizziness, and weight gain. However, for a more conclusive discussion about these side-effects, there needs to be a study of both short-term and long-term side effects, where the placebo groups don’t report the same side-effects as well.
  • Sleepiness and fatigue – Studies show that another common side effect of melatonin intake (in doses between 3 and 10mg daily) are sleepiness and fatigue. The side effects occurred in participants who took melatonin for several months. In one group, women who are post-menopausal breast cancer survivors reported cases of sleepiness, fatigue, and sleep disorders. In other studies, including adults and children, there were effects of excessive daytime sleepiness. The effects disappeared after two to three weeks of stopping melatonin intake.
  • Digestive issues – when it comes to melatonin side effects, vomiting and digestive issues seem to be rather common. The onset of these side effects is generally reported right after people start taking melatonin. It seems that melatonin can activate the receptors in the gastrointestinal tracts, and in turn cause some digestive disorders.
  • Cardiovascular issues – studies show that sleep medications and supplements containing melatonin induce arrhythmias and cardiovascular issues in patients who never had these health problems. There have also been cases of palpitations lasting for several weeks, as well as moderate hypotension or low blood pressure in children.
  • Restless legs syndrome – studies show that melatonin intake can worsen restless legs syndrome or the RLS. It can even play a role in the occurrence of RLS and aggravate the symptoms. The aggravation of the symptoms usually occurs in the evening or at night, when the melatonin secretion and effects take place.
  • Nightmares – Nightmares are one of the most frequently occurring side effects reported by the users. It seems that nightmares occur at regular melatonin doses, between 3 and 5mg, in both adults and children. The abnormal dreams are, however, not the only issue. There have been cases where people woke up from 4 hours of nightmares after taking melatonin. Nevertheless, the nightmares stopped occurring after patients stopped melatonin intake.
  • Irritability and mood changes – agitation, irritability, and mood changes often occur in patients who already have behavioral or psychiatric disorders, but began with melatonin intake. Daily intake of 2.5mg of melatonin for more than a year showed a cognitive decline, mood, behavior, and sleep disturbances in elderly people, as one study shows. The same results showed in trials with children, teenagers, and people with an intellectual disability or mental disorders.
  • Hypothermic effects – it is believed that daily high melatonin intake can lead to the lowering of body temperature. This phenomenon is explained by observing the natural melatonin production by the brain being in accordance with the lower body temperature. This means that the colder you feel, the sleepier you become. The same seems to apply to melatonin intake, only the difference being that it can lower the temperature abnormally, causing a hypothermic effect.
melatonion is not safe to eat while pregnant

Terry Cralle

Other Possible Melatonin Side Effects

  • Melatonin and birth control effects – melatonin supplements may not be safe for women trying to get pregnant. It seems that melatonin has similar effects as birth control, making it more difficult for women to reach ovulation and become pregnant. Some evidence shows that lower doses, up to 3mg are safe, but there is not enough research to prove that.
  • Melatonin and bleeding disorders – it is believed that regular melatonin intake can worsen the symptoms and effects of bleeding disorders. Studies show that melatonin may slow blood clotting or coagulation, which may lead to excessive bleeding and bruising.
  • Melatonin and epilepsy – studies and current data show that melatonin can trigger or worsen epilepsy and seizure frequency in some people. While some experts argue otherwise, some professionals do not recommend melatonin intake in people who are prone to having epileptic or other types of seizures; not even small doses.
  • Melatonin and transplant recipients – because melatonin can increase the immune function, it might interfere with immunosuppressive therapy used by transplant recipients.

Side Effects Of Melatonin Interactions

  • Sleepiness and drowsiness with sedative medication – the interaction between sedative medications or depressants and melatonin can lead to excessive daytime sleepiness and drowsiness. It is essential you avoid taking melatonin with medications like lorazepam, clonazepam, zolpidem, etc.
  • Wakefulness with caffeine – combining melatonin with caffeine may result in decreased melatonin effects. Caffeine will overpower melatonin, so instead of sleepy, one might feel more wakeful and alert.
  • Increased blood sugar with diabetes medication – because melatonin increases blood sugar levels, and the diabetic medication lowers it, it can completely overpower the effectiveness of diabetes medication. This can lead to some serious issues in diabetic patients, who should avoid taking melatonin with insulin, glimepiride, glipizide, rosiglitazone, etc.
  • Bleeding risk with anticoagulants – because melatonin slows down blood coagulation, it should be smart to avoid taking it together with medication that has the same effects. The combination of anticoagulants with melatonin may cause bleeding and bruising. Such medications include aspirin, ibuprofen, naproxen, enoxaparin, heparin, diclofenac, etc.

Melatonin FAQs

Who Shouldn’t Take Melatonin?

When considering all the side effects and possible melatonin interactions with certain medication, the following groups should avoid taking melatonin;

  • People suffering from inflammatory or autoimmune diseases,
  • Pregnant or breastfeeding women,
  • Ovulating women trying to get pregnant,
  • People who have responsible jobs, where sleepiness and drowsiness can cause possible safety problems,
  • People with epilepsy or a history of seizures,
  • People with mood, behavior, or personality disorders,
  • People with bleeding disorders,
  • People with cardiac or blood pressure issues, etc.

When Should I Use Melatonin – And How Much?

Providing you do NOT belong to the aforementioned risk groups, you should take melatonin for the following reasons (in accordance with the doctor’s recommendations);

  • If you have trouble falling asleep; you should take 0.3 to 5mg dose
  • If you experience serious sleep deprivation; you should take 2 to 12mg dose
  • If you suffer from extended sleep deprivation or insomnia; you should take 2 to 3mg dose of controlled-release melatonin
  • If you have jet lag; you should take up to 8mg dose of controlled-release melatonin
  • If you have high blood pressure; you should take between 2 and 3mg dose
  • If you have a solid tumor (without cysts or liquid); you should take 10 to 40mg dose
  • If you’re about to have surgery (you feel stressed and anxious); you should take 3 to 10mg dose
  • If you experience jaw joint and muscle pain; you should take 5mg dose

How Can I Increase Melatonin Levels Naturally?

To avoid the adverse effects of melatonin supplements, you can utilize the more natural ways of increasing melatonin levels in your body. Here are some recommendations;

  • Turn the lights off before sleep – avoid gadgets that emit blue or artificial light before sleep, since they will further lower your melatonin levels and make you feel awake instead of sleepy.
  • Go outside – by exposing yourself to natural daylight, your brain is more likely to produce higher levels of melatonin.
  • Eat healthy – make sure to eat foods that are high in melatonin and tryptophan, like leafy greens, lean/white meat, bananas, figs, dark chocolate, cottage cheese, etc.
  • Quit drinking and smoking – nicotine is known to inhibit melatonin synthesis, while alcohol diminishes its effects completely. Try to quit smoking, and at least do not drink before bedtime.

Final Thoughts

It is essential to mention that melatonin side effects do NOT occur in every single person who takes it. Some people process melatonin much better than the others. If you find yourself experiencing any of the aforementioned symptoms, make sure to stop taking melatonin and address the issues with your doctor. Also, before you even start taking melatonin, make sure to discuss the appropriate dose with your doctor.

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Tuesday 3rd of January 2023

It would be nice to have references. With each side effect is it significant ie one in 100 people or not significant one in 100,000. Melatonin has tons of studies of benefit. Just like any drug there are many side effects listed, does that mean you will get them? Let's not throw out the baby with the bathwater. Good to know possible side effects and if you have them stop using melatonin.


Monday 5th of September 2022

I've had severe rls for months, can't sleep more that 3-4 hrs a night, started getting headaches. Was taking 10 mg Melatonin each night. I'm stopping completely, see if it makes a difference. I'm a trucker, so I have to get sleep to function. Crossing me fingers, this works.....

Sandra DeJoe

Saturday 20th of August 2022

I had my 86 year old husband in a rehap center due to a bad fall, he was doing okay and I was able to sit and visit him and then they put him on melatonin to help him sleep his dementia has gotten so b ad after I brought him home, I am unable to get anyone to com e in and help. He is just out of my control.

Honey Bee

Saturday 11th of June 2022

I’ve been giving my 84 year old mom with dementia 1 mg of melatonin every night to help her sleep so I could get a good nights sleep for probably two months. It seems as if her dementia has gotten worse. I didn’t think that 1 mg would do anything to her. I wonder if she can at least get to like she was 2 months ago.

Arthur St Thomas

Sunday 5th of June 2022

I have been taking melatonin for about three months. I started with 10mg. I increased to 20mg. Started sleeping great except one night I got up to pee and lost comlete control of my body. Here is what it felt like; I felt like a man in a 40 ft boat in the middle of the ocean in a major storm with 60 foot waves trying to walk from the back of the boat to the front without anything to hold on to. I had no control of my body falling all over the place. When I do bench presses at the gym and pull myself up my head is spinning for a few moments. My equalibrium is way out of wack. I now realize after researching melatonin side effects this might be the cause. I've stopped taking melatonin. Hopefully these side effects will go away soon.