Melatonin and heart failure: what the study really shows, and what has happened since

By Tyler Smith, RN, BSN, BA · Updated October 17, 2026

Last checked October 17, 2026: still no full journal paper

The headline vs the fine print

The study made news again in August 2026 when it was reposted online, but the data had not changed.¹ Here is what it actually measured.

What the study looked at

Researchers used a large database of health records from many countries. They found about 130,000 adults with insomnia. The average age was about 56, and about 6 in 10 were women.^1,2

• Half had melatonin in their records for at least a year.
• The other half never had melatonin in their records. The two groups were matched on age, health problems, medicines, and more.²
• People who already had heart failure, or who took prescription sleeping pills, were left out.²
• Both groups were followed for 5 years.

What it found, per 100 people

One odd detail: more people were counted in the hospital for heart failure than were newly diagnosed with it. The researchers said this came from the way related medical codes were counted.¹ That is one more reason to read the numbers with care.

Three reasons the link may not be about melatonin

1. Poor sleep itself. A large study in Norway found that people with several insomnia symptoms had a much higher chance of heart failure over time.³ Everyone in this study had insomnia, and those who needed melatonin for a year or more may have had the worst sleep.
2. Other health problems. Shortness of breath at night, stress, pain, and low mood can all break up sleep. Someone with early heart trouble may sleep badly and reach for melatonin before anyone finds the heart problem.
3. Who gets it written down. In many countries, melatonin in a medical record means a doctor was involved. People who see doctors more often for sleep may be sicker overall. The researchers could not fully account for this.¹

None of this means the study is wrong. It means the study raised a question it was not built to answer.

What has happened since

The US National Center for Complementary and Integrative Health says melatonin appears safe for most adults in the short term, but that good data on long term use is lacking.⁶ That is still the honest summary.

5 questions to ask about any scary health headline

• Did it show cause, or just a link? Health record studies can only show a link.
• Who was studied? These were adults with insomnia, not everyone who takes melatonin.
• Was the dose known? Here it was not.
• Was it peer reviewed? A meeting abstract is an early step, not the final paper.
• What do other studies say? One study is a signal to watch, not a verdict.

My take as a nurse

Sleep doctors agree. The American College of Physicians recommends cognitive behavioral therapy for insomnia, often called CBT for insomnia, as the first step for long term sleep trouble.⁸ The American Academy of Sleep Medicine does not recommend melatonin on its own for chronic insomnia.⁷

Talk to your doctor first if

• You have heart failure, heart disease, or a heart rhythm problem.
• Heart failure runs in your family.
• You have high blood pressure or diabetes, or take medicine for either one. Read melatonin and blood pressure.
• You take blood thinners or other sleep medicine.
• You have taken melatonin every night for a year or more.

Please do not stop or change any prescribed medicine on your own because of this study. Bring it to your next visit and make a plan together.

Signs of heart failure to know

Whether or not you take melatonin, call your doctor if you notice these. The American Heart Association lists them as warning signs:⁹

• Shortness of breath, mostly when you lie down or are active.
• Swelling in your feet, ankles, legs, or belly.
• Feeling tired all the time.
• A cough or wheeze that will not go away.
• Fast weight gain over a few days.
• A fast or uneven heartbeat.

If you have chest pain, severe shortness of breath, or you faint, call 911 right away.

If you choose to use melatonin

1. Know your reason. Melatonin is a timing signal that tells your body night has started. It is not a sleeping pill.
2. Start low. In one study of adults over 50, just 0.3 mg brought night levels back to normal, while 3 mg pushed levels far higher.¹⁰ Many store products hold 5 mg to 10 mg. Read is 1 mg of melatonin enough.
3. Set an end date. Check in after a few weeks. If it is not helping, stop. If you want to keep going, talk to your doctor.
4. Build the habits. Same bedtime, same wake time, dim lights at night, and your phone out of bed.⁸

For a wider look at safety, read is melatonin bad for you and can melatonin make sleep worse.

Tyler Smith, RN, BSN, BA is a registered nurse and the founder of Driffly. He writes and reviews the articles in the sleep education hub. About Tyler

The author is the founder of Driffly, which sells the product mentioned in this article. This article is for education and is not medical advice. *These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.