Testosterone enanthate

Anabolic steroids

Also known as Test E, Delatestryl, Xyosted

The reference long-acting testosterone ester, and the backbone of most replacement regimens.

How it works

A testosterone molecule with a seven-carbon ester attached, which makes it oil-soluble enough to sit in a muscle depot and release slowly. The ester is cleaved off in circulation, leaving plain testosterone to act on the androgen receptor.

IntramuscularSubcutaneous

In the body

Half-life

4.5 days

Time to peak

2 d

90% gone after

14.9 d

Builds up to

1.52×

Steady state after about 22.8 d at weekly, often split into two injections.

Shape of a single dose, modelled as one compartment with first-order absorption. The peak is normalised to 100% because bioavailability and volume of distribution are not published for most of these compounds.

4.5 days, measured after intramuscular injection in oil. This is the depot-release rate, not the clearance of testosterone itself, which is a matter of minutes to hours. The injection site is what governs the curve.

What happens, and when

0 min, 24 hEster still largely in the depot; little has reached circulation.
24 h, 3 dLevels climbing towards peak.
3 d, 7 dThe plateau most of the week is spent in.

Doses

50 mg, 100 mgweekly, often split into two injectionsApproved label

Replacement dosing for diagnosed hypogonadism. Splitting the weekly amount across two injections flattens the peak-to-trough swing.

100 mg, 150 mgweeklyClinical trial

Studied in supraphysiological-dose trials. Above replacement, the dose-response for muscle continues but so does the rise in haematocrit and the fall in HDL.

Vial sizes

2000 mg2500 mg

Side effects

Raised haematocrit, which is the most common reason to reduce a dose
Acne and oily skin
Oestradiol-driven effects: water retention, gynecomastia
Testicular atrophy and reduced fertility
Accelerated male-pattern hair loss in those predisposed
Mood and sleep changes
Monitor: Haematocrit, androgens raise red cell mass, and the rise is dose-dependent
Monitor: Blood pressure
Monitor: Lipids, especially a fall in HDL
Monitor: Total and free testosterone, LH and FSH
Monitor: Oestradiol, for the aromatising compounds

Cautions

Prostate or breast cancer
Trying to conceive, suppression of spermatogenesis is the expected effect
Untreated severe sleep apnoea
Polycythaemia
Pregnancy

Status

Prescription-only in most countries and a controlled substance in many, including Schedule III in the United States. Banned in sport by WADA at all times.

Sources

Reference information for personal record-keeping. Not medical advice, and not a recommendation to use any of these compounds.