Sustanon 250 is an injectable blend of four testosterone esters dissolved in peanut oil. Each 1 mL ampoule contains 250 mg of esters, which works out to 176 mg of actual testosterone. The idea behind the blend is that a short ester raises testosterone quickly while longer esters keep it up for longer, so one injection can cover about three weeks.
In the UK it has been licensed since 1973 for testosterone replacement in men with confirmed hypogonadism, and as supportive therapy for transgender men. It has never been approved by the US FDA. Researchers studying anti-doping methods describe it as a product known to be misused by athletes (Solheim et al., Front Physiol 2020).
This page summarizes what the UK product label, clinical studies and regulators report. It is for education only and is not medical advice.
| Property | Detail |
|---|---|
| Drug class | Androgen; blend of four testosterone esters |
| Brand / authorization | Sustanon 250 (UK licence PL 39699/0059, first authorized February 1973; holder Aspen Pharma Trading) |
| Route | Deep intramuscular injection |
| Strength | 250 mg of esters per 1 mL ampoule, equal to 176 mg testosterone |
| Labeled adult dose (UK) | Usually 1 mL every 3 weeks |
| Half-life | No single value; testosterone peaks 24–48 h after a dose and falls to the lower limit of normal in ≈21 days (label) |
| Carrier | Refined arachis (peanut) oil with 100 mg/mL benzyl alcohol |
| US status | Not FDA-approved; testosterone and its esters are Schedule III controlled substances |
What it is
Sustanon 250 contains four esters of testosterone. An ester is a fatty side chain attached to the testosterone molecule. It makes the hormone more fat-soluble, so it seeps out of the oil depot in the muscle slowly. Once in the blood, the ester is cut off and ordinary testosterone is released (UK SmPC).
Heavier esters make up more of each milligram, so less of the labeled dose is testosterone. Using molecular weights from PubChem, the four components break down as follows:
| Ester | Amount per mL | Ester molecular weight | Share that is testosterone | Testosterone delivered |
|---|---|---|---|---|
| Testosterone propionate | 30 mg | 344.5 g/mol | ≈84% | ≈25 mg |
| Testosterone phenylpropionate | 60 mg | 420.6 g/mol | ≈69% | ≈41 mg |
| Testosterone isocaproate | 60 mg | 386.6 g/mol | ≈75% | ≈45 mg |
| Testosterone decanoate | 100 mg | 442.7 g/mol | ≈65% | ≈65 mg |
| Total | 250 mg | — | ≈70% | ≈176 mg |
The 176 mg total matches the figure stated on the label. Testosterone itself weighs 288.4 g/mol.
The label says only that the four esters have “different durations of action.” In a blood study after a single Sustanon 250 injection, the individual esters peaked within 24–72 hours, with timing that varied between people and with the length of the ester side chain (Forsdahl et al., Drug Test Anal 2015; summarized in Solheim et al., Front Physiol 2020). The single-ester versions are covered separately: testosterone propionate, phenylpropionate, isocaproate and decanoate.
Once released, the hormone is the same testosterone delivered by testosterone cypionate or enanthate. It acts on the androgen receptor directly and is also converted to dihydrotestosterone (DHT) and estradiol.
Pharmacokinetics
The label reports these values for a single 1 mL dose:
| Measure | Value |
|---|---|
| Peak total testosterone (Cmax) | ≈70 nmol/L (≈2,000 ng/dL) |
| Time to peak (tmax) | ≈24–48 h |
| Return to lower limit of the male normal range | ≈21 days |
| Binding to plasma proteins and SHBG (in vitro) | Over 97% |
| Metabolites | DHT and estradiol |
| Excretion | Mainly urine, as conjugates of etiocholanolone and androsterone |
Source: UK SmPC. 1 nmol/L of testosterone ≈ 28.8 ng/dL.
Independent studies show the same pattern:
- Hypogonadal men, 250 mg mixed esters. A 1984 UK study in 9 hypogonadal men found a mean peak of 71 nmol/L at 24–48 hours, followed by a steady decline to baseline after 2–3 weeks. On a three-weekly schedule the average level across the interval was 27.7 nmol/L. Estradiol also peaked above the normal male range, at a mean of 347 pmol/L (Cantrill et al., Clin Endocrinol 1984).
- Healthy young men, one Sustanon 250 injection. In a randomized, placebo-controlled study, total testosterone rose from 19.8 to 81.4 nmol/L 24 hours after the injection. Estradiol rose from 63.5 to 99.0 pmol/L, and LH (the pituitary signal to the testes) fell from 3.8 to 1.6 IU/L (Solheim et al., Front Physiol 2020).
- Every two weeks. A randomized crossover trial in 15 hypogonadal men gave 250 mg mixed esters every 2 weeks. It found “marked but reproducible” week-to-week swings in free and total testosterone (Conway et al., Int J Androl 1988).
In short, the blend does not create a flat level. A dose gives a high early peak followed by a decline over two to three weeks. The label gives no single half-life for the product.
Approved medical use
The UK Summary of Product Characteristics (SmPC) lists two uses (UK SmPC):
- testosterone replacement therapy for male hypogonadism, when the deficiency has been confirmed by clinical features and blood tests;
- supportive therapy for transgender men (female-to-male).
| Population | Labeled dose |
|---|---|
| Adults, including the elderly | Usually 1 mL every 3 weeks, adjusted to response |
| Transgender men | Specialist centers have used 1 mL every 2 weeks to 1 mL every 4 weeks |
| Children and adolescents | Safety and efficacy not adequately established |
The label recommends checking testosterone at baseline and at regular intervals to keep levels in the normal range. It also suggests the following checks before treatment, every three months for the first year, and yearly after that:
- prostate exam and PSA (prostate-specific antigen);
- hematocrit (the share of blood made up of red cells) and hemoglobin.
In treated hypogonadal men, the label reports increases in bone mineral density and lean mass, a decrease in fat mass, and improved libido and erectile function.
Regulatory status
- UK. Licensed since February 28, 1973. The current holder is Aspen Pharma Trading Limited (UK SmPC).
- US. The FDA’s approved-drug database (Drugs@FDA) lists no Sustanon product, and no product containing testosterone decanoate, isocaproate or phenylpropionate (openFDA Drugs@FDA). Testosterone and its salts, esters and ethers are Schedule III anabolic steroids under federal law (21 CFR 1308.13(f)).
- Sport. The label warns that athletes in sports governed by the World Anti-Doping Agency (WADA) should consult the WADA Code, because Sustanon 250 can interfere with anti-doping tests.
What the research shows
Sustanon 250 has no large outcome trials of its own. The controlled data come from small studies that used it as their testosterone source.
Men on long-term glucocorticoids
Fifteen men with asthma on long-term glucocorticoid (steroid anti-inflammatory) treatment were randomized to Sustanon 250 mg once a month or no treatment for 12 months, then crossed over for another 12 months (Reid et al., Arch Intern Med 1996):
| Outcome | During testosterone | During control period |
|---|---|---|
| Lumbar spine bone density | +5.0% | No change |
| Fat mass | Control-period gain reversed | +2.1 kg |
| Lean mass | Control-period loss reversed | −1.4 kg |
Markers of bone turnover also fell on testosterone.
Men with osteoporosis and normal testosterone
An open, uncontrolled study gave 23 men aged 34–73 with spinal fractures Sustanon 250 every 2 weeks for 6 months; 21 completed it (Anderson et al., Bone 1996; Anderson et al., J Bone Miner Res 1997):
| Measure | Change over 6 months |
|---|---|
| Lumbar spine bone density | 0.799 → 0.839 g/cm² (+5%) |
| Hip bone density | No change |
| Hematocrit | 43.4% → 45.6% |
| HDL cholesterol | −0.087 mmol/L (≈ −3.4 mg/dL) |
| Triglycerides | −0.405 mmol/L |
| Serum testosterone / estradiol | +55% / +45% |
The rise in spine density correlated with the rise in estradiol, not with testosterone. With no control group, these results are preliminary.
Older men doing resistance training
In a randomized, double-blind trial, 18 healthy older men (65–75) with normal testosterone received Sustanon 250 mg or saline every 2 weeks during 6 weeks of supervised weight training (Gharahdaghi et al., J Cachexia Sarcopenia Muscle 2019):
| Outcome | Testosterone + training (n = 9) | Placebo + training (n = 9) |
|---|---|---|
| Total fat-free mass | 53.0 → 56.0 kg | 54.1 → 54.8 kg (not significant) |
| Total fat mass | 22.5 → 21.3 kg | 24.7 → 24.5 kg (not significant) |
| Muscle protein synthesis | 2.13%/day | 1.34%/day |
Strength gains were also significantly larger with testosterone. Serum testosterone in the treated group rose from about 235 ng/dL at baseline to about 1,149 ng/dL by week 5, well above the normal range. The authors reported no adverse events, but a 6-week trial with 9 treated men cannot detect uncommon harms.
Type 2 diabetes with low testosterone
A double-blind crossover trial gave 20 hypogonadal men with type 2 diabetes Sustanon 200 mg or placebo every 2 weeks for 3 months each (Kapoor et al., Eur J Endocrinol 2007). Testosterone lowered leptin and adiponectin (hormones made by fat tissue) and reduced waist circumference. It did not change C-reactive protein, TNF-alpha or IL-6.
A single dose and athletic performance
In the same Danish anti-doping study described above, 19 young men received one Sustanon 250 injection or placebo. Despite testosterone levels about four times baseline, there was no improvement 24 hours later in jump height, 30-second cycle sprint power, or isometric arm strength (Solheim et al., Front Physiol 2020).
Side effects and risks
Labeled adverse reactions
The label lists reactions seen with androgen therapy in general (UK SmPC). It notes that side effects cannot be reversed quickly by stopping, because the depot keeps releasing hormone.
| Frequency | Reactions |
|---|---|
| Common (1 in 100 to 1 in 10) | Weight gain; raised hematocrit, hemoglobin and red cell count |
| Rare | Pulmonary oil microembolism |
| Frequency not known | Polycythemia, fluid retention, high blood pressure, mood changes, depression, nervousness, libido changes, nausea, abnormal liver tests, acne, itching, muscle pain, gynecomastia, low sperm count, priapism, prostate enlargement, raised PSA, progression of hidden prostate cancer, lipid changes |
In women, the label warns of virilization: hoarseness, acne, excess hair growth, menstrual changes and hair loss. Voice changes may be permanent.
Red blood cells
Raised hematocrit, hemoglobin and red cell count are listed as common on the label. In the osteoporosis study above, it rose from 43.4% to 45.6% on 250 mg every 2 weeks. In the Danish study, two 250 mg injections three weeks apart flagged the athlete blood passport as suspicious in 6 of 9 treated men (Solheim et al., Drug Test Anal 2020). The label adds that combining testosterone with SGLT-2 inhibitors (a class of diabetes drugs) has been linked to a higher risk of erythrocytosis.
Peanut oil and injection reactions
- Peanut and soya allergy. The product contains refined arachis (peanut) oil. The label contraindicates it in people allergic to peanuts or soya.
- Pulmonary oil microembolism. Rarely, oil reaches the lungs during or right after injection. This causes cough, shortness of breath, chest pain, dizziness or fainting. The label says these reactions are reversible and asks that patients be observed during and after each injection.
- Benzyl alcohol. Each mL contains 100 mg. It must not be given to premature babies or newborns.
Suppression of natural testosterone and fertility
Outside testosterone shuts down the body’s own production. In healthy young men, LH fell by more than half within 24 hours of a single injection (Solheim et al., Front Physiol 2020). In another study of 6 healthy young men, Sustanon lowered LH, the men’s own testosterone and INSL3 (a marker of the testosterone-producing Leydig cells); all three returned to baseline after treatment stopped (Albrethsen et al., JCEM 2023). The label lists oligospermia (low sperm count) and warns that androgens can impair male fertility.
Heart and blood vessels
The label warns that testosterone may raise blood pressure. It may also cause fluid retention, with or without heart failure, in people with severe heart, liver or kidney disease. It also advises caution in people with thrombophilia or risk factors for blood clots, citing post-marketing reports of deep-vein thrombosis and pulmonary embolism.
The label states that abuse of testosterone, usually at doses above the approved range and combined with other steroids, has caused serious cardiovascular, liver and psychiatric events, some fatal. A published case report describes a massive heart attack in a 26-year-old man with no classic risk factors who had used Sustanon 250 mg weekly for 6 months (Alrabadi et al., Biomed Rep 2020). A single case cannot prove cause, but it is consistent with the label’s warning.
Interactions
The label lists these interactions:
- Coumarin anticoagulants (e.g. warfarin). High doses of androgens may strengthen their effect, so prothrombin time should be monitored closely.
- Insulin and other diabetes drugs. Androgens may improve glucose tolerance and lower the dose needed.
- ACTH or corticosteroids. These may increase edema.
- Enzyme inducers and inhibitors. These may lower or raise testosterone levels.
- Thyroid tests. Total T4 may fall because binding protein drops, but free thyroid hormone is unchanged.
Who should not use it
The label contraindicates Sustanon 250 in:
- pregnancy and breastfeeding;
- known or suspected prostate or breast cancer;
- allergy to any ingredient, including peanut oil, and in people allergic to peanuts or soya.
It also advises caution with high blood pressure, sleep apnea, epilepsy, migraine, and in pre-pubertal children, where androgens can close growth plates early.
Legal status and use outside medicine
In the US, Sustanon 250 is not an approved drug, and any testosterone ester is a Schedule III controlled substance. Product sold outside a pharmacy is not regulated for dose, sterility or identity.
The label states that testosterone abuse can lead to dependence, with withdrawal symptoms after a large dose reduction or abrupt stop. For anti-doping, intact testosterone esters can be detected in blood after a Sustanon injection, which proves the testosterone came from outside the body (Forsdahl et al., Drug Test Anal 2015).
Key takeaways
- Four esters, one hormone. Each 1 mL ampoule holds four testosterone esters that deliver 176 mg of ordinary testosterone. The esters only change how fast it is released.
- Not actually flat. A dose peaks at about 70 nmol/L within 24–48 hours and declines to the low-normal range over about three weeks. The label gives no single half-life.
- A UK-licensed TRT drug, not a US one. It has been licensed in the UK since 1973 at usually 1 mL every 3 weeks. It has never been FDA-approved, and testosterone esters are Schedule III in the US.
- Small studies, consistent effects. Studies using it report more lean mass, less fat and higher spine bone density. All were small, and some were uncontrolled.
- Peanut oil matters. It is contraindicated in peanut or soya allergy, and oil microembolism after injection is a rare labeled reaction.
- Hematocrit and suppression are expected. Red cell counts rise, and LH and natural testosterone fall within a day of a single dose.
Sources
- Aspen Pharma Trading Limited. Sustanon 250, 250mg/ml solution for injection: Summary of Product Characteristics. PL 39699/0059; revised December 2025. emc.
- National Center for Biotechnology Information. PubChem compound summaries: testosterone (CID 6013), testosterone propionate (CID 5995), testosterone phenylpropionate (CID 14743), testosterone isocaproate (CID 231084), testosterone decanoate (CID 155143). PubChem.
- Cantrill JA, Dewis P, Large DM, Newman M, Anderson DC. Which testosterone replacement therapy? Clin Endocrinol (Oxf). 1984;21(2):97–107. PubMed.
- Conway AJ, Boylan LM, Howe C, Ross G, Handelsman DJ. Randomized clinical trial of testosterone replacement therapy in hypogonadal men. Int J Androl. 1988;11(4):247–264. PubMed.
- Forsdahl G, Erceg D, Geisendorfer T, et al. Detection of testosterone esters in blood. Drug Test Anal. 2015;7(11-12):983–989. PubMed.
- Solheim SA, Mørkeberg J, Juul A, et al. An intramuscular injection of mixed testosterone esters does not acutely enhance strength and power in recreationally active young men. Front Physiol. 2020;11:563620. PubMed.
- Solheim SA, Mørkeberg J, Dehnes Y, et al. Changes in blood parameters after intramuscular testosterone ester injections: implications for anti-doping. Drug Test Anal. 2020;12(8):1019–1030. PubMed.
- Reid IR, Wattie DJ, Evans MC, Stapleton JP. Testosterone therapy in glucocorticoid-treated men. Arch Intern Med. 1996;156(11):1173–1177. PubMed.
- Anderson FH, Francis RM, Faulkner K. Androgen supplementation in eugonadal men with osteoporosis: effects of 6 months of treatment on bone mineral density and cardiovascular risk factors. Bone. 1996;18(2):171–177. PubMed.
- Anderson FH, Francis RM, Peaston RT, Wastell HJ. Androgen supplementation in eugonadal men with osteoporosis: effects of six months’ treatment on markers of bone formation and resorption. J Bone Miner Res. 1997;12(3):472–478. PubMed.
- Gharahdaghi N, Rudrappa S, Brook MS, et al. Testosterone therapy induces molecular programming augmenting physiological adaptations to resistance exercise in older men. J Cachexia Sarcopenia Muscle. 2019;10(6):1276–1294. PubMed.
- Kapoor D, Clarke S, Stanworth R, Channer KS, Jones TH. The effect of testosterone replacement therapy on adipocytokines and C-reactive protein in hypogonadal men with type 2 diabetes. Eur J Endocrinol. 2007;156(5):595–602. PubMed.
- Albrethsen J, Østergren PB, Norup PB, et al. Serum insulin-like factor 3, testosterone, and LH in experimental and therapeutic testicular suppression. J Clin Endocrinol Metab. 2023;108(11):2834–2839. PubMed.
- Alrabadi N, Jarrah MI, Alzoubi KH. Acute myocardial infarction with cardiogenic shock in a young physically active physician concurrently using the anabolic steroid sustanon: a case report. Biomed Rep. 2020;13(3):14. PubMed.
- US Food and Drug Administration. Drugs@FDA dataset, queried via openFDA for testosterone decanoate, isocaproate and phenylpropionate and for the brand name Sustanon (no matches). openFDA.
- Drug Enforcement Administration. Schedules of controlled substances: Schedule III, paragraph (f), anabolic steroids. 21 CFR 1308.13. eCFR.