Summary. Studies have demonstrated that melatonin has significant effects on ischemia-reperfusion injury, myocardial chronic intermittent hypoxia injury, pulmonary hypertension, hypertension, valvular heart diseases, vascular diseases, and lipid metabolism.
Furthermore melatonin has been shown to have valuable effects on cardiovascular health, blood pressure, and endothelial function and it might benefit patients with heart failure.
While melatonin is generally considered safe, there have been some reports of it causing heart palpitations in certain individuals. This may be due to the fact that melatonin can lower blood pressure, which can cause the heart to beat faster to compensate.
Signs of melatonin overdose include excessive sleepiness, vomiting and trouble breathing. Other side effects of both low and high doses of melatonin can include headaches, excessive sleepiness, blood pressure changes, gastrointestinal problems, changes in other hormone levels and mood problems, McCall says.
Regardless of whether it truly helps with sleep or not, Dr. Ramkissoon doesn't recommend taking melatonin long-term.
Melatonin is generally safe for short-term use. Unlike with many sleep medications, with melatonin you are unlikely to become dependent on it, have less response to it after repeated use or experience a hangover effect. The most common melatonin side effects include: Headache.
Do not use melatonin if you are pregnant or breastfeeding or have an autoimmune disorder, a seizure disorder or depression. Talk to your health care provider if you have diabetes or high blood pressure.
Symptoms of Melatonin Overdose
Generally, an adult dose is thought to be between 1 and 10 mg. Doses near the 30 mg mark are usually considered to be harmful.
Anything over 10 mg for adults and 5 mg for children is too much melatonin. Taking too much melatonin can cause dizziness, headaches, and lethargy. It can also have a negative effect on your sleep cycle, leading to temporary or even permanent trouble sleeping.
Arrhythmogenesis decreases during nighttime when the melatonin levels increase 30 to 70 folds. Life-threatening cardiac arrhythmias (ventricular tachycardia, ventricular fibrillation, and sudden cardiac death) are more likely to occur in the morning after waking.
Melatonin inhibits angiotensin II–induced atrial fibrillation through preventing degradation of Ang II Type I Receptor–Associated Protein (ATRAP)
If you're experiencing symptoms of an allergic reaction, shortness of breath, chest pain, or a rise in blood pressure after taking melatonin, you should seek emergency health services immediately.
A person using melatonin should contact their local emergency number if they experience any of the following side effects: extremely high blood pressure. shortness of breath. sudden chest pain.
Melatonin's target sites are both central and peripheral. Binding sites have been found in many areas of the brain, including the pars tuberalis and hypothalamus, but also in the cells of the immune system, gonads, kidney, and the cardiovascular system (39, 40).
In the UK and most of Europe, it's classed as a medicine, not a health supplement and as such, requires a prescription. This is because melatonin is considered “medical by function” which means that it requires a drug licence.
Melatonin is generally safe for most people, and many people won't experience major complications when taking too much. Even so, an overdose can cause unpleasant side effects. Keep your dose to no more than 1 to 3 mg per night.
How Long Does Melatonin Stay in Your System? The half-life of melatonin is between 20 and 50 minutes, meaning half of the initial dosage in the body is eliminated after that amount of time. In total, melatonin stays in your system for about four to five hours.
Is it possible to overdose on melatonin? In short: no. There's no good evidence that taking too much melatonin can lead to a life-threatening overdose the way other sedating drugs can.
Dangerous interactions could occur
The supplement could also interfere with other important medications, including blood thinners, diabetes drugs, immune system-suppressing drugs, anti-seizure drugs and some contraceptives.
In several clinical trials, melatonin was found to be well tolerated and not associated with serum enzyme elevations or evidence of liver injury. Despite wide scale use, melatonin has not been convincingly linked to instances of clinically apparent liver injury.
In this context, melatonin can regulate heart rate (87), and reduce nocturnal blood pressure in patients with hypertension (88, 89). Moreover, melatonin may serve as a potent protective agent in the cardiovascular system, and diminish the risk of developing reperfusion injury after myocardial infarction (90).
This may include cramps, nausea, and diarrhea. Dizziness Some people who take melatonin also report mild dizziness, lightheadedness, or vertigo. Irritability Too much melatonin can also affect mood. You may feel cranky, anxious, or have periods of depression.
These studies strongly suggest that melatonin protects the heart and blood vessels. Importantly, patients who have had a heart attack have reduced nighttime melatonin levels.