Melatonin is the hormone the pineal gland, deep in the brain, releases in darkness to set the body’s day-and-night rhythm. Light at night suppresses it, and the World Health Organization’s International Agency for Research on Cancer classifies night shift work as probably causing cancer in humans, in part for this reason.1 Melatonin has been studied alongside cancer treatment for more than 30 years, mostly in Italy. This article explains how it may act against cancer, what the trials show, the doses used, and safety.
How Melatonin May Act Against Cancer
In laboratory studies, melatonin acts as an antioxidant, restores the body’s daily rhythm, supports natural killer cells and other immune cells, slows the growth of new blood vessels that feed tumors, and interferes with estrogen signaling in breast cancer cells. These effects explain the interest, but what matters is what happens in people.
The Italian Trials
Most of the early trials came from Paolo Lissoni and colleagues in Monza, Italy. In one, 100 patients with metastatic lung cancer received cisplatin and etoposide chemotherapy, with or without 20 mg of melatonin each evening. More tumors shrank in the melatonin group, chemotherapy was better tolerated, and three of 49 patients taking melatonin were alive at five years, while no patient on chemotherapy alone survived beyond two years.2
A Canadian meta-analysis of 21 randomized trials found that adding melatonin reduced deaths at one year by 37 percent, increased the number of tumors that shrank, and reduced side effects of chemotherapy, including fatigue, low platelet counts, nausea and nerve damage.3 The limitation is that most of these trials came from one research group and were not blinded.
Newer Blinded Trials
Later trials that compared melatonin with a placebo, without patients or doctors knowing who received which, have been less positive. In Thailand, 151 patients with advanced lung cancer receiving chemotherapy took 10 or 20 mg of melatonin or a placebo; survival did not differ, although quality of life tended to be better with melatonin.4 In the Canadian AMPLCaRe trial of patients after lung cancer surgery, a year of nightly melatonin did not reduce recurrence overall, with a possible benefit in more advanced stages that needs confirmation.5
Sleep and Side Effects
Randomized trials have found that melatonin improves sleep in people with advanced cancer, helps protect thinking and mood in women receiving chemotherapy for breast cancer, and may protect the kidneys from damage caused by cisplatin. Results for cancer-related fatigue have been mixed.6
Doses Used in Studies, and Safety
Most cancer trials used 10 to 20 mg taken at bedtime. Melatonin is generally well tolerated. The most common side effects are drowsiness, morning grogginess, headache, dizziness and nausea, so it is taken only at night. It can interact with blood thinners such as warfarin, sedatives and sleeping pills, drugs that suppress the immune system, and diabetes medicines.
Protecting natural melatonin matters too: a dark bedroom, little screen light late at night, and a regular sleep schedule. See our articles on vitamin D and cancer and the guide to repurposed drugs.
How Cancer Expert MD Helps
Cancer Expert MD provides education and consultation for people with every type and stage of cancer, and specializes in Stage IV and metastatic cancer. Our book, The New Reality of Cancer, covers melatonin and more than 50 repurposed drugs, vitamins and plant compounds, with how each works, the pathways it blocks, what studies in people show, the doses used, and drug interactions.
Frequently Asked Questions
Does melatonin help people with cancer live longer?
Italian trials and a meta-analysis of 21 trials found fewer deaths at one year, but newer placebo-controlled trials in Thailand and Canada did not find a survival benefit.
Can melatonin reduce chemotherapy side effects?
Trials have found improvements in sleep, low platelet counts, nerve damage and nausea, and possible protection of the kidneys from cisplatin. Results for fatigue are mixed.
What doses were used in studies?
Most cancer trials used 10 to 20 mg at bedtime.
Is melatonin safe?
It is generally well tolerated. The main side effects are drowsiness and morning grogginess, and it can interact with blood thinners, sedatives, immune-suppressing drugs and diabetes medicines.
About the author. Dr. Silver, MD, graduated from Temple University School of Medicine, trained as an interventional cardiologist, and has practiced medicine for nearly fifty years. A lymphoma survivor of about twenty-five years, he is co-author, with Dr. Lindmeier, DHSc, of The New Reality of Cancer: The Science of Recovery. Read more about Dr. Silver, MD.
Research by Dr. Lindmeier, DHSc, cancer educator and co-author of The New Reality of Cancer.
This article is for general education only and is not individual medical advice. Always consult your own doctor before making any changes to your care.
© 2026 Lovely LYF LLC. All rights reserved. This article draws on the research in The New Reality of Cancer and may not be copied, republished or distributed without written permission.
For more in-depth information on this topic and many others, get our book, The New Reality of Cancer: The Science of Recovery.
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References
- International Agency for Research on Cancer. Night shift work. IARC Monographs on the Identification of Carcinogenic Hazards to Humans, Volume 124. 2020.
- Lissoni P, Chilelli M, Villa S, Cerizza L, Tancini G. Five years survival in metastatic non-small cell lung cancer patients treated with chemotherapy alone or chemotherapy and melatonin: a randomized trial. Journal of Pineal Research. 2003;35(1):12–15.
- Seely D, Wu P, Fritz H, et al. Melatonin as adjuvant cancer care with and without chemotherapy: a systematic review and meta-analysis of randomized trials. Integrative Cancer Therapies. 2012;11(4):293–303.
- Sookprasert A, Johns NP, Phunmanee A, et al. Melatonin in patients with cancer receiving chemotherapy: a randomized, double-blind, placebo-controlled trial. Anticancer Research. 2014;34(12):7327–7337.
- Seely D, et al. Adjuvant melatonin for the prevention of recurrence and mortality following lung cancer resection (AMPLCaRe): a randomized placebo-controlled clinical trial. EClinicalMedicine. 2021.
- Melatonin in cancer: mechanisms and clinical evidence, review of randomized clinical trials. Frontiers in Pharmacology. 2025.
This article is for education only. It is not medical advice and does not diagnose or treat any condition. Cancer Expert MD has no financial relationship with any laboratory, drug maker, supplement company, clinic or hospital.
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