Danazol dosage and evidence
Written by Aaron CuhaReviewed Sep 2026
The short answer
Danazol is the one drug here that made telomeres longer in people.
Evidence grade for Danazol: Limited. The rule: people have taken it in a published study, but fewer than 100 of them. The sum on this page: 3 completed trials, 63 people given it. A grade counts how much has been done to people, not whether it works.
- People given it
- 63
- Human studies
- 3
- Found nothing
- 0
Dose
Approved medicine. No human dose established for unlabelled uses
Labeled amounts sit on the prescribing information. This page records what trials measured, not a personal dose.
FDA approved for endometriosis, lumpy (fibrocystic) breast disease and hereditary angioedema, an inherited swelling disorder. It carries a boxed warning, the FDA's strongest kind. Not approved for telomere disease, ageing or any longevity use. Its use in inherited telomere diseases is off label, and it was studied under an investigational plan.
5 effects reported, 4 unwanted, 1 wanted, by people using it, not a trial
Goal pages: Ageing and longevity, Heart and circulation
In plain English
In plain English, from Aaron
This is how I would explain it to a friend. The evidence, with the numbers, is further down the page.
Danazol is a man-made male hormone. It is approved for endometriosis and an inherited swelling condition, and it carries the FDA's strongest warning. In one study, it made telomeres longer in people with a rare inherited disease. Telomeres are the caps on the ends of your DNA.
What people take it for
- Making telomeres longer.
- Slowing ageing, based on that telomere result.
- Treating bone marrow failure from telomere disease.
What studies in people showed
One study gave 27 people with inherited telomere disease 800 mg a day. It was stopped early. In 11 of the 12 people who could be measured at two years, telomeres got longer, by 386 base pairs on average. Blood counts improved in 19 of 24 checked at 3 months. There was no comparison group. Liver enzymes rose in 41 percent, and 33 percent got cramps. Years later, the blood count gains faded about 1.6 years after stopping. No healthy person has been studied, and nobody measured ageing.
What people report
Reports, not study results
The good
- We have no user reports of a benefit. Forum talk rests almost only on the 2016 telomere study.
The bad
- Male-hormone effects are the main complaint: weight gain, acne, a deeper voice, and male traits in women. Some do not go away.
- In the study, liver enzymes rose in 41 percent and a third got muscle cramps.
- Pancreatitis has been reported in people taking it for telomere disease.
- Home-made plans often skip the liver checks doctors do as standard.
Where these come from: Longevity forums and patient groups for aplastic anaemia and telomere disease, as collected on this page. The liver, cramp and pancreatitis lines are from the studies on this page.
My bottom line
A real result in a rare disease, with real costs. It is a male hormone with the FDA's strongest warning. For a healthy person chasing longer telomeres, I would not touch it.
An opinion, not a finding. I am a coach, not a doctor.
What it has been measured to do
Measured in people
Goals Danazol has been tested for in people, biggest studies first. We count only what the studies on this page say, so the real numbers may be higher.
- Cholesterol and blood fats36 people · 1 study
- Blood pressure36 people · 1 study
- Heart attacks and strokes36 people · 1 study
- Biological age markers27 people · 2 studies
- Living longer12 people · 1 study
What people using it report
Real people telling you what happened to them. Nobody checked it, and the people who post are not a fair sample, so it cannot prove anything works. It is still the best guide on this page to what people actually do with Danazol, what they expect, and what goes wrong. The full account, including the negative reports, is below.
31 of the 36 indexed goals have no study of any kind behind Danazol
No study in people, animals or cells on this page reports a result for these. That does not prove Danazol does nothing for them. It does mean anything you have heard about Danazol and one of these did not come from a study cited here.
Show full evidence
What is Danazol?
Danazol is the one drug here that made telomeres longer in people. Telomeres are the caps on the ends of your DNA that shorten with age. In a study of 27 people with inherited telomere disease, 11 of the 12 who could be measured gained length after 24 months, 386 base pairs on average. The study was stopped early. Telomere length is a lab marker, and nobody measured lifespan.
Danazol is a man-made male hormone. It was approved decades ago for endometriosis, breast lumps and hereditary angioedema, an inherited swelling condition. It reached ageing research through blood doctors, who have long used male hormones for bone marrow failure. Someone noticed that sex hormones turn up the telomere-building gene in cells and animals.
The study that made its name was run at the US National Institutes of Health. 27 people with inherited telomere diseases took 800 mg of danazol a day, planned for 24 months. In these diseases the body cannot keep up its telomeres. That leads to bone marrow failure, liver scarring and lung scarring. The goal was to slow yearly telomere loss by 20 percent at 24 months.
The study was stopped early. Telomere loss had slowed in all 12 people who could be measured for the main goal. Counting all 27 who started, 12, or 44 percent, met the goal. Then came the surprise. 11 of those 12, or 92 percent, did not just lose length more slowly. Their telomeres grew, by 386 base pairs on average. Blood counts improved in 19 of 24 people who could be checked at 3 months.
That is a striking result, and it is important to be exact about its limits. These people had a gene defect that breaks telomere upkeep. Telomere length was the thing measured. Nobody measured lifespan, healthy years, physical function or deaths, and no healthy person was studied.
How does Danazol work?
Danazol is a man-made hormone with weak male-hormone effects. It turns down the hormone signals from the brain to the ovaries and testes, and it sticks to several hormone receptors. The telomere idea is separate from what it is approved for. In cells and animals, sex hormones turn up TERT, the working part of telomerase, the enzyme that rebuilds telomeres. The body can turn male hormones into estrogen, and estrogen switches on the TERT gene. Raising telomerase in blood-forming cells is the likely route to the telomere gain. This is a hormone acting on a gene. It is not a telomerase drug.
What have studies in people found about Danazol?
One small study in inherited telomere disease that found longer telomeres. Also a long-term follow-up of the same patients, and side effect reports from other illnesses. No study in healthy people, and no study that measured an ageing outcome.
- 27 people signed up. Everyone got the drug, 800 mg a day, and there was no dummy pill group. It was planned for 24 months and stopped early, because the telomere goal was met in everyone who could be measured.
- Counting all 27 who started, 12 met the main goal. Only 12 people could be measured for it at 24 months. The headline result rests on those 12.
- 11 of those 12 gained telomere length rather than just losing it more slowly. The average gain was 386 base pairs. Similar gains showed up at 6 and 12 months in side analyses.
- Blood counts improved in 19 of 24 who could be checked at 3 months, and 10 of 12 at 24 months. For these patients, that is a real health gain.
- Side effects in the study: mild to moderate rises in liver enzymes in 41 percent and muscle cramps in 33 percent. Outside the study, people have had pancreatitis. In people with aplastic anaemia, good cholesterol fell 30 percent and the heart's main pumping chamber changed after 6 months.
- Nobody has given danazol to healthy people to test an ageing outcome. No study has tested whether it helps anyone live longer or stay healthy for longer.
What this does not tell you: Stopping a study early because a lab marker looks good makes the effect look bigger than it is. Everyone involved knows this. That is why the paper gives both figures: 12 of 27 who started, and 12 of 12 who could be measured. There was no comparison group, so nobody saw what these patients' telomeres would have done without the drug. Most important, these patients have a gene defect in telomere upkeep. They have a specific reason to respond to a telomere boost. Telomeres shortening in a healthy person is not the same thing. There is no evidence that making them longer in a healthy person does any good.
What do people who took Danazol report?
This is what real people say happened to them, good and bad. Nobody measured it. A report cannot tell a real effect from the lift people get just from expecting it to work, from a diet or training change made at the same time, or from what was really in the vial. We still put it near the top. It is the next best thing to a study in people: what happens when real people use it, including what goes wrong.
- Longevity forums talk about it almost only because of the 2016 telomere result. They usually leave out how many people were in it, the early stop, and the disease those people had.
- Where doctors use it, male-hormone effects are the main complaint. That means weight gain, acne, a deeper voice, and in women, male traits. Some of these do not go away.
- Doctors check liver enzymes as standard on danazol. Home-made plans often skip that.
Sources: Longevity forums and patient communities in aplastic anaemia and telomere biology disorders. Uncontrolled self-report, and the patient communities are describing a different population from the people considering it for ageing.
The state of the research
Any old drug used for something new raises two separate questions, and they have different answers. First: does the drug do what it was approved to do? Here, big studies in sick people settle that. Second: does it slow ageing in people? No study has tested that. A strong answer to the first question says nothing about the second. Treating the approved use as part proof that it slows ageing is the biggest mistake in this field.
Danazol is the exception that shows how strict the bar has to be. It gave a real, convincing and surprising result in people. Telomeres got longer, in a disease where they shrink too fast. That result deserves to be taken seriously. The usual line on this site, that there is no human evidence, would be wrong here.
What it is not is proof that danazol slows ageing. Telomere length is a lab marker, and a disputed one. It gets measured because it can be. It only loosely tracks age. Drugs that change it have again and again failed to change anything a person would notice. The study measured telomeres and blood counts over 24 months in 27 people with an inherited disease. It did not measure survival, function or healthy years, and it included nobody without the disease.
There is also a risk that longevity articles rarely mention. Cancers use telomerase to keep growing. In patients whose disease already raises their cancer risk, doctors judged the trade worth it, with specialists watching. In a healthy person taking a hormone to lengthen telomeres, it is an untested bet the other way.
The side effects are the rest of the honest picture. In the study, liver enzymes rose in 41 percent and 33 percent got cramps. Outside it, a 2025 study in aplastic anaemia found good cholesterol down 30 percent and bad cholesterol up 11 percent after 6 months. The heart's shape and pumping changed too. A 2024 Mayo Clinic report describes pancreatitis in people taking danazol for telomere disease. Danazol is a male hormone with the FDA's strongest warning label, and it acts like one.
The evidence, in charts
Fig. 1a · how many people
75people, across 3 studies in people cited here
| Study | People | Share |
|---|---|---|
| Blood Cells, Molecules and Diseases 2025 | 36 | 48% |
| New England Journal of Medicine 2016 | 27 | 36% |
| Blood Advances 2026 | 12 | 16% |
Counts are the number of people each study on this page says it signed up. That includes studies that only watched people and gave nobody the compound. 2 more studies in people give no headcount and are not counted here. Studies still signing people up are left out, and only studies cited on this page are counted.
Fig. 1b · evidence mix
All 5 sources here are studies in people.
- Study in people · done in people5100%
Counted from the list of sources on this page. It counts only what we cite, so there may be more studies out there. A review counts once, however many studies it sums up.
Fig. 2 · evidence over time
The studies cover 4 different years, 2016 to 2026, counted from the list of sources on this page.
Fig. 3 · legal status at a glance
US
Approved
UK
Approved
AU
Approved
CA
Approved
Approved in all four countries shown. This is what the law says, not a verdict on the science. See Legal status below for the full text and any notes.
Fig. 5 · what the molecule is
- Kind of compound
- Hormone
- Molecule weight
- 337.5 Da
- Half-life
- About 4.5 hoursShort, 1 to 6 hours
- Chain length
- None on file
Half-life as stated on file: About 4 to 5 hours after a single dose, with longer estimates reported on repeated dosing.
No amino acid sequence is on file for Danazol, which is expected: a hormone is not built from amino acids.
The studies we cite
- Study in people2016Danazol Treatment for Telomere Diseases
Danazol stopped telomeres shrinking, and the trial was halted early because it appeared to be working. 27 patients with inherited telomere disease took 800 mg a day by mouth, planned for two years. Everyone got the drug and there was nothing to compare against. Telomere loss slowed in all 12 patients assessable on the main measure, and 12 of the 27 met it. 11 of those 12 gained length by two years, averaging 386 base pairs. Liver enzymes rose mildly in 41 percent and a third got muscle cramps.
The result that makes danazol interesting. Phase 1 to 2 prospective study, 27 patients with inherited telomere diseases, danazol 800 mg a day orally for a planned 24 months, primary efficacy endpoint a 20 percent reduction in annual telomere attrition. Halted early because attrition was reduced in all 12 patients evaluable for the primary endpoint; 12 of 27 (44 percent) met it in intention to treat. 11 of 12 (92 percent) gained telomere length at 24 months against baseline, mean increase 386 base pairs. Haematological response in 19 of 24 evaluable at 3 months and 10 of 12 at 24 months. Grade 2 or lower elevated liver enzymes in 41 percent and muscle cramps in 33 percent.
- Study in people2016Danazol for Genetic Bone Marrow and Lung Disorders
This is the registry record for that study, and it adds no new result. It is listed as completed, with 27 people actually enrolled, running from July 2011 to November 2016. The record confirms two things the paper says: everyone got the drug, and the enrolment figure is what was published.
The registration for the New England Journal of Medicine study. Listed as completed with an actual enrolment of 27, running from July 2011 to November 2016. The registry confirms the single-arm design and the enrolment figure reported in the paper.
- Study in people2026Danazol treatment for telomere biology disorders: long-term results of a phase 1/2 study
The follow-up answers the question the early stop left open. The same 26 patients were tracked for a median of 3.3 years afterwards. Once danazol stopped, the improvement in blood counts lasted a median of 1.6 years and then went. Lung capacity held steady on the drug and fell away after withdrawal. Half the group was still alive 7.7 years after enrolling, and 16 of the 26 had died by the last check, most often of infection. The benefit is real, and it does not outlast the drug.
Long-term follow-up of the same National Institutes of Health cohort, published as a brief report ten years after the original. Median follow-up 3.3 years. After danazol was stopped, median time to loss of haematologic response was 1.6 years in 12 evaluable patients. Median event free survival 5.7 years and median overall survival from enrolment 7.7 years, with 16 of 26 patients (62 percent) dead at last follow-up, infection the commonest known cause. Lung function was stable on the drug and declined after withdrawal, and 6 of 7 who restarted responded again. The original trial was stopped early on a biomarker, and this is the durability answer that early stop left open: the benefit does not outlast the drug.
- Study in people2025Danazol causes significant changes in the cardiometabolic profile of patients with acquired aplastic anaemia
This is what danazol costs, measured in a different illness. 36 patients with acquired aplastic anaemia took danazol on its own, 10 mg per kilogram a day up to a cap of 600 mg. After six months, good cholesterol had fallen 30 percent and bad cholesterol had risen 11 percent. The size of the heart's main pumping chamber changed, as did how well it pumped and relaxed. The authors conclude the drug causes severe blood fat changes and possible heart damage. Different condition, same drug, similar dose.
The cost side, in a different indication. 36 patients with acquired aplastic anaemia on danazol monotherapy at 10 mg per kg per day capped at 600 mg. After 6 months HDL cholesterol fell 30 percent and LDL rose 11 percent, with significant changes in left ventricular mass, ejection fraction and diastolic indices. The authors conclude that danazol causes profound dyslipidaemia and potential cardiac dysfunction.
- Study in people2024Pancreatitis as a Potential Consequence of Danazol Therapy for Telomere Biology Disorders
A serious side effect surfaced years after the trial was over. Doctors at the Mayo Clinic describe pancreatitis, an inflamed pancreas, in people taking danazol for telomere biology disorders. It was published eight years after the original trial. This came out of ordinary clinical use, not from a study set up to count side effects. Nobody can tell from a report like this how often it happens.
A Mayo Clinic report describing pancreatitis in the setting of danazol therapy for telomere biology disorders, published eight years after the original trial. An adverse effect identified in ongoing clinical use rather than in the trial.
Common questions
Has Danazol been tested in people?
Yes. 63 people given it across 3 completed trials cited here, 0 of which found nothing. Danazol is the one drug here that made telomeres longer in people.
What is the Danazol dosage?
Approved medicine. No human dose established for unlabelled uses. Labeled amounts sit on the prescribing information. This page records what trials measured, not a personal dose. FDA approved for endometriosis, lumpy (fibrocystic) breast disease and hereditary angioedema, an inherited swelling disorder. It carries a boxed warning, the FDA's strongest kind. Not approved for telomere disease, ageing or any longevity use. Its use in inherited telomere diseases is off label, and it was studied under an investigational plan.
Is Danazol FDA-approved?
FDA approved for endometriosis, lumpy (fibrocystic) breast disease and hereditary angioedema, an inherited swelling disorder. It carries a boxed warning, the FDA's strongest kind. Not approved for telomere disease, ageing or any longevity use. Its use in inherited telomere diseases is off label, and it was studied under an investigational plan.
Did danazol really lengthen telomeres in humans?
Yes, and this site does not say that lightly. In the 2016 US government study, 11 of 12 patients who could be measured at 24 months gained telomere length. The average gain was 386 base pairs. All of them had an inherited telomere disease. Everyone got the drug, there was no dummy pill group, and the study was stopped early.
Does that mean it slows ageing?
No. Telomere length is a lab marker, not a health outcome. The study measured telomere length and blood counts over 24 months in 27 people with a gene defect in telomere upkeep. It did not measure lifespan, healthy years, physical function or deaths. No healthy person has been studied.
Why was the trial stopped early?
At the halfway check, telomere loss had slowed in all 12 patients who could be measured for the main goal. Stopping early when a lab marker is moving the right way tends to make the effect look bigger than it is. That is part of why the paper also gives the figure for everyone who started: 12 of 27, or 44 percent.
What are the side effects?
In the study, mild to moderate rises in liver enzymes in 41 percent and muscle cramps in 33 percent. In wider use, male-hormone effects, including male traits in women. The US warning label covers pregnancy, blood clots, blood-filled pockets in the liver, and raised pressure around the brain. A 2025 study in aplastic anaemia found good cholesterol down 30 percent and measurable heart changes after 6 months. Pancreatitis has also been reported in people taking it for telomere disease.
Is it better than telomere supplements?
It is the only thing in this area with a published result of longer telomeres in people. That really does set it apart from supplements sold on cell data. It is also a prescription male hormone with the FDA's strongest warning label. It was studied for two years in 27 people with a rare inherited disease. Those are not the same comparison, and neither one supports taking it for ageing.