Anastrozole
A non-steroidal aromatase inhibitor used to control oestradiol on aromatising cycles. Effective and well studied — with over-suppression, not under-dosing, the more common error.
01 Overview
Anastrozole reversibly inhibits the aromatase enzyme, lowering conversion of testosterone to oestradiol. Its clinical pedigree is in breast cancer, where the dosing is far higher than needed alongside a cycle.
The defining mistake with it is crushing oestradiol too low, which causes its own joint, libido, mood and lipid problems.
02 Mechanism
Competitive, reversible aromatase inhibitor. Lowers systemic oestradiol at source, unlike a SERM which blocks the receptor in specific tissues.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| On-cycle | 0.25–0.5 mg/wk | Oral | Titrated against a sensitive oestradiol assay — never on a fixed schedule. |
Ester comparison
| Ester | Half-life | Injection freq. | Testosterone by mass |
|---|
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Controls oestradiolCounters gynaecomastia, water retention and related blood-pressure rise | Dose-dependent | Clinical | |
| Reduces water retentionBy lowering oestrogenic fluid retention | Moderate | Observational |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Over-suppression of oestradiolThe main hazard — joint pain, low libido, poor lipids, low mood and bone loss from crushing oestradiol too far. | Moderate | Common | Clinical |
06 Commonly used with
What anastrozole is combined with, and why. This is about intent rather than safety — the interactions table below covers what is dangerous. Nothing here is listed without what it costs.
| Compound | Frequency | Purpose & trade-off |
|---|---|---|
| Support & ancillaries | ||
| Testosteronearomatising base | Dose-titrated alongside testosterone to blunt the aromatisation that drives estrogenic water retention and gynecomastia.Trade-off: Over-suppression crashes estradiol, degrading lipids, joint comfort, mood and libido. | |
| Dianaboloral kickstart | Added during high-dose methandienone use to control the heavy estrogen conversion that oral pushes.Trade-off: Dianabol also raises BP and strains the liver, effects an AI does nothing to address while estrogen control can mask fluid overload. | |
| Testosterone Propionatecontest prep | Used into a show to keep estrogen and subcutaneous water minimal for a drier look on stage.Trade-off: Aggressive estrogen suppression near a show can flatten muscle fullness and spike joint pain. | |
| hCGon-cycle | Paired with hCG because hCG stimulates intratesticular aromatisation, and the AI offsets that added estrogen load.Trade-off: Stacking two hormonal manipulations makes estradiol harder to dial in and easy to overshoot in either direction. | |