Mifepristone dosage and evidence
Written by Aaron CuhaReviewed Sep 2026
The short answer
In people, mifepristone is approved for high blood sugar in Cushing's syndrome and for ending early pregnancy.
Evidence grade for Mifepristone: Moderate. The rule: at least one finished study in people, and at least 100 people who took it. The sum on this page: 2 completed trials, 320 people given it. A grade counts how much has been done to people, not whether it works.
- People given it
- 320
- Human studies
- 2
- 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 as Korlym for high blood sugar caused by too much cortisol in Cushing's syndrome. Also FDA-approved as Mifeprex to end a pregnancy with medicine. Not approved for any ageing use.
4 effects reported, 3 unwanted, 1 wanted, by people using it, not a trial
Goal pages: Fat loss and metabolism, Brain, memory and mood, Ageing and longevity, Injury, healing and recovery, Heart and circulation, Bone and joints, Sleep, Gut health
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.
Mifepristone blocks the body's cortisol and progesterone signals. It is approved for high blood sugar in Cushing's syndrome and for ending early pregnancy. Some thought blocking cortisol might slow ageing.
What people take it for
- Slowing ageing by blocking the stress hormone cortisol.
- Guarding muscle, bone and brain against cortisol.
What studies in people showed
Nobody has tested it for ageing in people. In 50 adults with Cushing's syndrome, it improved blood sugar, blood pressure and weight over six months. There was no group to compare with. In 270 women, paired with a second drug, it ended early pregnancies. Now mice. It did not make male or female mice live longer.
What people report
Reports, not study results
The good
- In Cushing's syndrome, where cortisol is the problem, blood sugar and weight got better.
The bad
- Tiredness, nausea, headache and low potassium were common in the Cushing's study.
- Cortisol rises on it, so normal blood tests mislead.
- It ends pregnancy.
Where these come from: The side effects are from the Cushing's study and drug notes on this page. We have no user reports.
My bottom line
Blocking cortisol with a drug did nothing for mice. Handle stress with sleep and training. This is not a longevity drug, and it is dangerous to play with.
An opinion, not a finding. I am a coach, not a doctor.
What it has been measured to do
Measured in people
Goals Mifepristone 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.
- Gut and digestion270 people · 1 study
- Losing weight50 people · 1 study
- Blood sugar and insulin50 people · 1 study
- Pain50 people · 1 study
- Energy and fatigue50 people · 1 study
- Blood pressure50 people · 1 study
Animal and lab work, not yet tested in people
Real results, but from animals or cells, not people. What works in a mouse often does not work the same way in a person. This is an approved medicine. So the missing study in people is for this use, not for the drug. Drug makers paid to test it for what it is approved for. The record on this one is set out below.
- Living longer1 animal or lab study
29 of the 36 indexed goals have no study of any kind behind Mifepristone
No study in people, animals or cells on this page reports a result for these. That does not prove Mifepristone does nothing for them. It does mean anything you have heard about Mifepristone and one of these did not come from a study cited here.
Show full evidence
What is Mifepristone?
In people, mifepristone is approved for high blood sugar in Cushing's syndrome and for ending early pregnancy. Nobody has tested it for ageing. Blocking cortisol was a serious idea for slowing ageing, because years of too much cortisol damage muscle, bone and brain. In mice, the NIA lifespan test found nothing in either sex.
The reason anyone tested this is worth stating, because it is a good idea. Cortisol, the stress hormone, rises with age. Years of too much of it cause the very changes that make ageing go badly: muscle loss, bone loss, more belly fat, insulin resistance, shrinking of a memory area of the brain (the hippocampus) and a weaker immune system. Block cortisol's receptor, and those should slow.
Mifepristone is the tool on hand. It strongly blocks the receptors for both cortisol and progesterone. It is already approved for high blood sugar in Cushing's syndrome, where the body makes too much cortisol. Separately, and with much debate, it is approved for ending pregnancy.
In the mouse lifespan program's 2026 run, it did not make male or female mice live longer. That is the answer the idea got when it was tested properly.
How does Mifepristone work?
Mifepristone sits on the cortisol receptor and blocks it, so cortisol cannot switch on its genes. It also blocks the progesterone receptor, which is the basis of its use in pregnancy. At the cortisol receptor, it stops the signals that break down muscle, make the liver release sugar and move fat around the body. Because it blocks the receptor and does not lower cortisol, blood cortisol actually goes up on treatment. The body senses the blocked signal and makes more. That matters a lot for doctors keeping track of it.
What have studies in people found about Mifepristone?
A long record as an approved drug for two unrelated uses, and nothing at all on ageing.
- Approved for ending pregnancy, because it blocks progesterone. In 270 women up to 63 days pregnant, mifepristone and then misoprostol ended the pregnancy without surgery in 95 percent when the second drug went in the vagina, and 87 percent when swallowed.
- Approved for high blood sugar in Cushing's syndrome, where blocking the cortisol receptor is the whole point. In 50 adults with Cushing's, HbA1c (a three month blood sugar average) fell from 7.43 to 6.29 percent over 24 weeks, with no comparison group.
- Known risks of blocking the cortisol receptor: symptoms like failing adrenal glands, low potassium, and a thicker womb lining.
- Because it blocks the receptor and does not lower the hormone, blood cortisol rises during treatment. So the usual cortisol test cannot be used to keep track of it.
- No human study has looked at lifespan, healthy years, muscle loss with age, or anything else about ageing.
What this does not tell you: There is no human ageing data, and the mouse lifespan answer was no. Because it also blocks progesterone, it is a poor tool for testing the cortisol idea in anyone who could get pregnant. Outside its approved uses, it is a poor idea in general.
The state of the research
This compound was one of eleven in the program's run reported in 2026. None of the eleven clearly made male or female mice live longer. The run is worth seeing as a whole. It deliberately retested astaxanthin, mitoglitazone and meclizine. The same program had earlier found all three made mice live longer. This time they were given at different doses or started at older ages, and all three failed. In females, pooling all three labs, astaxanthin, late-start mitoglitazone and pioglitazone were linked to clearly shorter lives. A closer look found that untreated females at one lab lived unusually long. With that lab left out, the harm held for mitoglitazone and pioglitazone only. The authors conclude that timing and dose matter a great deal, and that results from one lab or one run need careful reading.
The useful thing about this failure is that it reins in a popular story. People say all the time that stress and cortisol drive ageing, and the case for how that would work is truly strong. Blocking the receptor for a lifetime in mice should have been the clean test, and it did nothing. That does not disprove the cortisol story. A blunt lifelong block of a hormone the body needs is not the same as cutting back too much of it. But it does mean the obvious drug version of the idea has been tried and has failed.
The National Institute on Aging runs the Interventions Testing Program at three separate labs: The Jackson Laboratory, the University of Michigan and the University of Texas Health Science Center at San Antonio. It uses UM-HET3 mice, a mixed breed made by crossing four strains, so a result cannot be a quirk of one strain. Compounds go in the food. Both sexes are tested. Each group is big enough to spot about a 10 percent change in lifespan. Results are checked with one test for typical lifespan and another for the longest-lived mice. The failures are published next to the wins. No other ageing research has all of that together. That is why a no from this program means much more than a no from one lab.
The evidence, in charts
Fig. 1a · how many people
320people, across 2 studies in people cited here
| Study | People | Share |
|---|---|---|
| The New England Journal of Medicine 1995 | 270 | 84% |
| The Journal of Clinical Endocrinology and Metabolism 2012 | 50 | 16% |
One study holds 84% of these people, so the total rests more on one study than its size suggests. 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. Studies still signing people up are left out, and only studies cited on this page are counted.
Fig. 1b · evidence mix
2 of 3 sources here are studies in people. The rest is not.
- Study in people · done in people267%
- Animal study · done in animals133%
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 3 different years, 1995 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
- Small molecule
- Molecule weight
- 429.6 Da. A steroidal small molecule, not a peptide.
- Half-life
- About 18 hoursMedium, 6 to 24 hours
- Chain length
- None on file
Half-life as stated on file: Roughly 18 hours in the terminal phase, after a slower initial distribution, so once-daily dosing is used clinically.
No amino acid sequence is on file for Mifepristone, which is expected: a small molecule is not built from amino acids.
The studies we cite
- Study in people2012Mifepristone, a glucocorticoid receptor antagonist, produces clinical and metabolic benefits in patients with Cushing's syndrome.
In Cushing's syndrome, where cortisol is the problem, blocking its receptor with mifepristone improved blood sugar, blood pressure and weight over six months. 50 adults took part, and there was no dummy pill group. Tiredness, nausea, headache and low potassium were common. This is the approved use, not a study of ageing.
50 adults with endogenous Cushing's syndrome, after failed treatment, were given mifepristone 300 to 1,200 mg daily for 24 weeks, open-label, at 17 US centres. In the diabetes or impaired glucose tolerance group 60% had a glucose AUC response; HbA1c fell from 7.43% to 6.29% and fasting glucose from 149 to 105 mg/dL. In the hypertension group 38% had a diastolic pressure response. Mean weight change -5.7%; 87% judged clinically improved. Fatigue, nausea, headache, low potassium, arthralgia, vomiting, oedema and endometrial thickening were common.
- Study in people1995Induction of abortion with mifepristone (RU 486) and oral or vaginal misoprostol.
The other approved use. Mifepristone followed by misoprostol ended early pregnancies without surgery in nearly all of 270 women. Putting the second drug in the vagina worked better than swallowing it. Every woman got mifepristone. What was decided by chance was how the second drug was taken.
270 women seeking abortion within 63 days of amenorrhoea given 600 mg mifepristone, then randomised to 800 mcg misoprostol orally or vaginally. Complete expulsion without surgery in 95% vaginal versus 87% oral (p=0.03); continued pregnancy 1% versus 7% (p=0.01); abortion within 4 hours 93% versus 78% (p<0.001). Vomiting and diarrhoea more frequent with oral misoprostol.
- Animal study2026Astaxanthin, meclizine, mitoglitazone, pioglitazone, alpha-ketoglutarate, mifepristone, methotrexate, and atorvastatin-telmisartan do not increase lifespan
In mice. The NIA mouse lifespan program tested eleven compounds in mixed-breed mice at three labs. Mifepristone did not clearly make male or female mice live longer.
Interventions Testing Program, eleven compounds in genetically heterogeneous UM-HET3 mice at three sites. Mifepristone did not significantly increase lifespan in male or female mice.
Common questions
Has Mifepristone been tested in people?
Yes. 320 people given it across 2 completed trials cited here, 0 of which found nothing. In people, mifepristone is approved for high blood sugar in Cushing's syndrome and for ending early pregnancy.
What is the Mifepristone 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 as Korlym for high blood sugar caused by too much cortisol in Cushing's syndrome. Also FDA-approved as Mifeprex to end a pregnancy with medicine. Not approved for any ageing use.
Is Mifepristone FDA-approved?
FDA-approved as Korlym for high blood sugar caused by too much cortisol in Cushing's syndrome. Also FDA-approved as Mifeprex to end a pregnancy with medicine. Not approved for any ageing use.
Does blocking cortisol slow ageing?
Not in the one careful lifespan test. Mifepristone, a strong blocker of the cortisol receptor, did not make mice of either sex live longer in testing at several labs. The case that cortisol drives decline with age is still reasonable. The drug version of the fix did not work.
Is this safe to experiment with?
No, and it is one of the clearer no answers on this site. It blocks a hormone pathway the body needs. It makes cortisol rise, so routine tests mislead. It carries risks of adrenal failure-like symptoms and low potassium, and it is a strong drug for ending pregnancy. It has no ageing benefit to weigh against any of that.
Why is it in a longevity database at all?
Because the National Institute on Aging tested it as a way to live longer and published that it did not work. Recording that is the point of these pages.
Latest reading on Mifepristone
Blog posts about Mifepristone, newest first.