Peptide & Experimental
Metenolone (Primobolan)
Anabolic androgenic steroid (acetate taken orally, enanthate as an injection); approved in Japan · Primobolan, Primobolan Depot, methenolone, metenolone acetate, metenolone enanthate, Primo
Metenolone, known as Primobolan, is an anabolic androgenic steroid that is still approved in Japan today as a tablet for osteoporosis, severe wasting and anemia. In strength sports it is considered mild and well tolerated. In humans, however, it has barely been studied for this: there is no meaningful controlled trial, only small, old case series and the information in the prescribing information.
In short
Metenolone is a medicine with a long history and a thin body of studies. In Japan it is approved as Primobolan tablets, for osteoporosis, for severe wasting due to kidney disease, cancer, injuries or burns, and for bone marrow failure due to aplastic anemia. Our research found no controlled trials that support this; the data come from small series without a comparison group. The risks, by contrast, are documented: liver damage with jaundice, blood lipid disorders – in 12 of 28 treated women, one of them with a heart attack – and, in women, a voice change that is hardly reversible once advanced. The reputation as a mild steroid is a statement based on experience, not on studies.
What metenolone is and how it works
Metenolone is a synthetic derivative of dihydrotestosterone. There are two forms: metenolone acetate as a tablet and metenolone enanthate as a depot injection, both under the name Primobolan. Unlike oxymetholone or stanozolol, metenolone is not 17α-alkylated but methylated at position 1. In Japan, Primobolan is still approved as a tablet today; the prescribing information was last revised in 2020.
According to the Japanese prescribing information, metenolone promotes protein synthesis, inhibits protein breakdown and increases the retention of calcium and phosphorus; in small investigations, hemoglobin and red blood cells rose. Like all steroids, it also has a virilizing effect and suppresses testicular function with longer use. For comparison with a better-studied steroid, see the article on nandrolone; an overview is given in Anabolic steroids.
What is well supported
Little is well supported here, and that is the finding. What is established is the approval status in Japan with the indications and side effects listed there. Documented in humans are liver dysfunction and jaundice, blood lipid disorders in a small series, virilization in women with possibly permanent voice change, and suppression of testicular function. For the effect itself there are only small series without a comparison group.
What the studies show
Japanese prescribing information: indications and mode of action
The prescribing information for Primobolan tablets (as of 2020) lists osteoporosis, severe wasting in chronic kidney disease, cancer, injuries and burns, as well as bone marrow failure in aplastic anemia. As evidence for the mode of action, it cites small investigations in healthy people and in patients with osteoporosis, hormone deficiency or muscle diseases, in which nitrogen, calcium and phosphorus were retained and hemoglobin and red blood cells rose. It does not give frequencies for the side effects.
Lockner 1979: treatment-refractory anemia
In a series of 19 consecutive patients with anemia that did not respond to other treatments, remission occurred in 3 of 6 with pancytopenia, 2 of 4 with bicytopenia, 1 of 5 with refractory anemia and 1 of 4 with myelofibrosis. No prolongation of life was apparent in those who responded. There was no comparison group.
Garbrecht 1981: blood lipids in breast cancer
Of 28 postmenopausal women with metastatic breast cancer who additionally received metenolone by injection, 12 developed hyperlipoproteinemia, 10 of type IIa and 2 of type IIb. One of these patients suffered a heart attack during treatment. No relationship with the dose was found; after discontinuation, the lipid disorders resolved in all cases.
Velazquez 2004: liver tumors under androgens
The case collection on 133 liver tumors under androgens mainly names oxymetholone, methyltestosterone and danazol; however, tumors also occurred in patients who received only injections. The authors conclude that everyone treated with anabolic steroids carries a risk of liver tumors whose magnitude cannot be calculated. The Japanese prescribing information also mentions liver tumors after long-term, high-dose administration in aplastic anemia.
Where the data stop
- Effect in humans. Our research found no meaningful randomized trial of metenolone, neither in sick nor in healthy people.
- The reputation as a mild steroid. That metenolone is better tolerated than other steroids has not been tested in comparative studies in humans. The prescribing information lists the same groups of side effects as for other anabolic steroids, without frequencies.
- Heart and blood vessels. On the heart and blood vessels there is only the small series with 28 women. Long-term data are lacking.
- Injection and tablet. The Japanese approval concerns the tablet. There are hardly any recent data on the depot injection.
Status, approval and legal
In Germany, metenolone and its esters are prescription-only (German Ordinance on Prescription-Only Medicines, Annex 1). Our research did not find a finished medicinal product approved in Germany. In Japan it is approved as Primobolan tablets and is prescription-only.
Metenolone is listed in the Annex of the German Anti-Doping Act. Manufacturing, trading and supplying it for doping purposes are prohibited, as are acquiring and possessing non-small quantities for doping in sport; the penalty ranges up to three years, in serious cases up to ten. In sport it is on the WADA Prohibited List under S1.1 and is prohibited at all times.
Safety
Liver: Although metenolone is not 17α-alkylated, the Japanese prescribing information lists liver dysfunction with markedly elevated values and jaundice as serious side effects and calls for regular liver tests with longer use. Liver tumors have been described after long-term, high-dose administration of anabolic steroids.
Blood lipids and heart: In a series of 28 women, 12 developed a lipid metabolism disorder, and one suffered a heart attack. In heart and kidney disease, fluid retention can occur. Anticoagulants such as warfarin have a stronger effect.
Hormonal axis: In men, longer use suppresses testicular function, and sperm and seminal fluid decrease; impotence and persistent erection have been described. In women, the prescribing information lists hoarseness and voice change that is hard to reverse once advanced and is often preceded by menstrual irregularities, along with hair growth, acne and enlargement of the clitoris. Glucose tolerance may worsen.
Mental health: The prescribing information lists increased libido. For steroids as a whole, the Endocrine Society describes dependence, a withdrawal syndrome and mental disorders; more on this under Anabolic steroids. That hardly any data exist on metenolone does not mean it is safe, but that no one has examined it systematically. A conversation with a physician belongs before any step here.
BK-Score Long used, barely studied
| Human evidence | 3 | |
|---|---|---|
| Mechanism | 6 | |
| Safety data | 4 | |
| Hype gap | 3 | |
| Track record of use | 6 |
Evidence 3, because there is no meaningful controlled trial in humans: the data come from small, uncontrolled series, such as 19 patients with treatment-refractory anemia, some of whom responded, without any apparent prolongation of life (Lockner 1979), and from the information in the Japanese prescribing information; there is nothing on muscle mass or strength in healthy people. Mechanism 6, because the action via the androgen receptor and the retention of nitrogen, calcium and phosphorus have been described in humans, but only in small, old investigations. Safety 4, because liver damage, virilization and blood lipid disorders are documented (12 of 28 women with hyperlipoproteinemia, Garbrecht 1981), but the prescribing information gives no frequencies and systematic safety studies are lacking. Hype 3, because the reputation as a particularly mild, well-tolerated steroid is not based on comparative human studies. Use 6, because metenolone has been used medically for decades and is still approved in Japan today. Direction open: long use, but too few controlled data for a statement on benefit and risk.
The score rates the state of knowledge, not the substance. “Safety data 9” means well studied – not harmless. “Track record of use 9” means used long and widely – that is not proof of efficacy.
Subjective assessment by Biohacking Kompakt based on published scoring rules – not a scientific rating and not a medical recommendation. Rules and all ratings (German)
Frequently asked questions about metenolone
Is metenolone a mild steroid?
That is its reputation, but not a study result. There are no comparative studies in humans. The Japanese prescribing information lists liver damage, virilization and suppression of testicular function, as with other anabolic steroids.
What is metenolone approved for?
In Japan, as Primobolan tablets for osteoporosis, severe wasting due to kidney disease, cancer, injuries or burns, and for bone marrow failure due to aplastic anemia. Our research did not find a product approved in Germany.
Is metenolone bad for the liver?
It is not 17α-alkylated, yet the prescribing information lists liver dysfunction and jaundice as serious side effects. Liver tumors have been described after long-term, high-dose administration of anabolic steroids.
Can metenolone change women’s voices?
Yes. The prescribing information lists hoarseness and voice changes that are hard to reverse once advanced; menstrual irregularities often come first.
Is metenolone legal in Germany?
It is prescription-only. It is listed in the Annex of the German Anti-Doping Act; acquiring and possessing non-small quantities for doping is prohibited. In sport it is prohibited at all times.
Related
- Related topicOxymetholone (Anadrol)
- Related topicFluoxymesterone (Halotestin)
- Related topicStanozolol (Winstrol)
- Related topicNandrolone decanoate
- Related topicMethandrostenolone (Dianabol)
- Related topicDrostanolone (Masteron)
Sources
- Prescribing information for Primobolan tablets (metenolone acetate), Japan, as of 08/2020 – indications, side effects, mode of action (KEGG/JAPIC, in Japanese)
- Lockner D, Acta Med Scand 1979 – metenolone in treatment-refractory anemia, 19 patients
- Garbrecht M et al., Dtsch Med Wochenschr 1981 – hyperlipoproteinemia under metenolone in 28 women with breast cancer
- Velazquez I, Alter BP, Am J Hematol 2004 – androgens and liver tumors, case collection
- Pope HG et al., Endocr Rev 2014 – Endocrine Society: health consequences of performance-enhancing drugs
- German Ordinance on Prescription-Only Medicines (AMVV), Annex 1 – prescription requirement
- German Anti-Doping Act (AntiDopG), § 2 to § 4 and Annex
- Prohibited List in sport 2026: S1.1 anabolic androgenic steroids, prohibited at all times (WADA Prohibited List)
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Information only, not medical advice and not a usage or dosage recommendation. Prescription-only and unapproved substances belong in the hands of a physician. Last updated: 2026-10-05.