What is Methylstenbolone?
Methylstenbolone (M-Sten) is an oral, 17a-alkylated designer steroid from the prohormone/designer wave of the 2010s. It is very potent and delivers dry strength and mass gains without aromatization but, like all 17a-alkylated orals, is markedly liver-loading.
This information is for research and educational purposes only. No medical advice.
Comparison
Methylstenbolone and relatives
Closely related steroids with a methyl group at position 17, as described in the TPD lexicon. Tap a card to open its entry.
Simplified: methylstenbolone differs from methasterone only by a double bond in the first ring. Both often come in the same product. 104
How it works
Methylstenbolone activates the androgen receptor strongly and does not aromatize. Gains are dry and hard, the side effect profile harsh in line with the high potency - especially liver and lipids.
Where it acts
What was observed with methylstenbolone
Tap a point or a card. Liver from a case report, skin from reports after contaminated capsules, testes from a review on designer steroids.
- Liver
Jaundice from bile congestion after 30 days, peak only weeks after stopping1
Observed in trials - Skin and hair
Hair loss in buyers of capsules containing methylstenbolone and methasterone5
Observed in trials - Testes
Designer steroids described as a cause of hormone deficiency and infertility6
Observed in trials
Use and dosing
Dosing
Dosing, titration and syringe
Loading the dosing information …
- Getting started and stepping up, drawn as a staircase
- Units on the U-100 syringe for every step
- How long one vial lasts
What the research shows
As a designer steroid there are hardly any controlled human studies. The AAS pharmacology (Kicman 2008, Hartgens & Kuipers 2004) classes the properties of oral 17a-alkylated steroids.
Study results
What the trials measured
Interactive: switch tabs, tap points, show or hide arms. Arms are named relative to each other, no dosing advice.
Blood bilirubin after 30 days of intake1
Total bilirubin as a multiple of the lab's upper limit, days from the first day of intake
Case report, 26-year-old man: Day 35 +10.2-fold, Day 42 +11.5-fold, Day 43 +11.2-fold, Day 55 +16.8-fold, Day 59 +24.2-fold, Day 60 +20.4-fold, Day 89 +9.3-fold, Day 110 +1.1-fold.
Calculated from table 1 of the case report (total bilirubin divided by the lab's upper limit). Intake ended around day 30, the peak came on day 59. The biopsy showed bile congestion without scarring. A single case, not a trial.
How long methylstenbolone was detectable in urine23
Excretion studies with a single dose, figures in days (d)
45 hours are rounded to whole days. The values for breakdown products are lower limits: the first study still found them after a week, the second on day 29, the end of sample collection. These studies measure detection for doping control, not effects.
Research status
Where the research stands
Methylstenbolone was never tested in a clinical trial. ClinicalTrials.gov lists not a single trial, the literature consists of breakdown studies for doping control, analyses of dietary supplements and one case report. As of 26 Oct 2026. 9
- Preclinical Breakdown in human liver microsomes and in mice with human liver cells
- Phase 1 no registered trial
- Phase 2 no registered trial
- Phase 3 no registered trial
- Approval not yet
So far there is no registered trial in humans. 9
Side effects
- Liver: 17a-alkylated, strong - short cycles, liver support.
- Lipids: marked HDL lowering.
- Blood pressure rises.
- HPTA suppression - PCT topic.
Storage
Store dry and cool, protected from light. Out of reach of children.
