What Is Anadrol (Oxymetholone)? The Complete UK Bulking Guide (2026)

Anadrol — the brand name for oxymetholone — is the most powerful oral anabolic steroid currently in widespread use. Its capacity for rapid, dramatic mass and strength gains is unmatched among oral compounds, but it comes with the most significant toxicity profile of any commonly used anabolic steroid. Understanding exactly what Anadrol is, how it differs from other bulking compounds, and what its genuine risks are is non-negotiable before considering it.

What Is Anadrol (Oxymetholone)?

Oxymetholone is a synthetic anabolic-androgenic steroid derived from dihydrotestosterone (DHT), first developed in 1959 by Syntex Pharmaceuticals for the treatment of anaemia. It was approved by the FDA under the brand name Anadrol-50 and has remained in clinical use — primarily for aplastic anaemia, anaemia from myelofibrosis, and HIV-associated wasting — despite its significant toxicity profile.

Its anabolic-to-androgenic ratio is approximately 320:45 (testosterone = 100:100), indicating strong anabolic activity relative to androgenic effect on paper. In practice, oxymetholone produces some of the most pronounced androgenic side effects of any oral steroid due to its unique receptor profile and potent C-17aa alkylation.

How Anadrol Works: The Unique Mechanism

Oxymetholone's mechanism distinguishes it from most anabolic steroids in one critical respect: it does not exert its anabolic effects primarily through androgen receptor activation. Research has shown that oxymetholone's anabolic activity is largely mediated through oestrogen receptors — specifically, oxymetholone or one of its metabolites acts as a potent oestrogen receptor agonist in muscle tissue. This explains several of its unusual properties:

• It produces extreme mass gains (much of which is water and glycogen retention driven by oestrogen-receptor activity in muscle)
• It causes significant oestrogen-like side effects (water retention, gynecomastia risk) despite being technically non-aromatising
• Standard aromatase inhibitors are partially effective at controlling its oestrogen-like effects, but do not fully address them since the mechanism is not aromatisation per se

What Anadrol Does: Effects and Timeline

Anadrol is uniquely fast-acting for a mass-building compound. Users typically report:

• Week 1–2: Pronounced strength increase, rapid weight gain (often 5–10 lbs in the first two weeks, predominantly water and glycogen)
• Week 2–4: Continued strength gains; significant bodyweight increase; marked fullness and pump during training
• Week 4–6: Plateau in rate of gain; diminishing returns beyond 6 weeks

Total weight gain of 20–30 lbs during a 4–6 week Anadrol cycle is not uncommon in well-fed athletes — though a significant portion of this represents water retention rather than contractile muscle tissue. Strength gains are the most impressive aspect, with users regularly reporting personal records broken within the first two weeks.

Medical Uses of Oxymetholone

• Aplastic anaemia: Oxymetholone significantly stimulates erythropoiesis and is still used clinically for severe aplastic anaemia unresponsive to other treatments
• Myelofibrosis-associated anaemia: Reduces transfusion requirements in patients with bone marrow fibrosis
• HIV/AIDS wasting: Preserves and rebuilds lean mass in advanced HIV patients; studied in clinical trials with positive outcomes at 150–300 mg/day (far above performance doses)

Anadrol vs Dianabol: How Do They Compare?

Both are powerful oral bulking steroids, but they have distinct profiles. For a full head-to-head breakdown, see our Anadrol vs Dianabol comparison. The headline differences: Anadrol produces faster and more dramatic gains but carries higher hepatotoxicity, more severe side effects, and a worse lipid impact. Dianabol is more manageable for most users and more appropriate as an introductory oral bulking compound.

Who Should (and Should Not) Use Anadrol

Appropriate for:

• Experienced users with prior testosterone and Dianabol cycles who have established their baseline tolerance to anabolic steroids
• Athletes requiring maximum strength in a short window (4–6 weeks)
• Off-season bulk phases where rapid mass gain is the priority

Not appropriate for:

• Beginners — Anadrol is one of the least appropriate first-cycle compounds due to its side effect severity
• Anyone with pre-existing liver disease or elevated liver enzymes
• Anyone with cardiovascular risk factors, particularly hypertension
• Women — virilisation risk is extreme even at low doses
• Anyone planning a cycle longer than 6 weeks of oral use

For safer oral bulking alternatives, see our guide to the best oral steroids and our oral steroids complete guide. Browse available Anadrol products.

UK Legal Status

Oxymetholone is a Class C controlled substance. For a complete legal overview, see our UK steroid law guide.

Frequently Asked Questions

Is Anadrol the strongest oral steroid?

Oxymetholone is the most powerful oral anabolic steroid in widespread use for mass and strength gain. Its effects at 50–100 mg/day exceed those of any other commonly used oral anabolic compound. However, “strongest” comes with the most serious toxicity profile of any oral AAS.

Does Anadrol aromatise?

Not through the aromatase enzyme. However, oxymetholone or its metabolites appear to directly activate oestrogen receptors, producing oestrogen-like effects (water retention, gynecomastia risk). This means standard AIs do not fully address oestrogen-type side effects from Anadrol. SERMs (Nolvadex, Clomid) are more effective at blocking these effects at the receptor level.

Can you keep Anadrol gains?

The majority of rapid early weight gain from Anadrol is water and glycogen, which dissipates when the compound is stopped. Users who successfully maintain a caloric surplus and strong training programme while on Anadrol typically retain 50–60% of total weight gained as actual lean mass. Proper PCT further supports lean mass retention by restoring natural testosterone production. See our complete PCT guide.

How long before Anadrol starts working?

Anadrol is one of the fastest-acting oral steroids. Most users report noticeable strength increases and a feeling of enhanced pump within 3–5 days. Significant bodyweight increase becomes apparent by the end of the first week.