Winstrol Depot is the injectable form of stanozolol, the same 17α-methylated anabolic-androgenic steroid sold as oral Winstrol tablets. It is a 50 mg/mL suspension of stanozolol itself, not an ester, injected into muscle.

In the US, injectable stanozolol is listed only as a veterinary drug. Federal regulations list a 50 mg/mL suspension for dogs, cats and horses, and Drugs@FDA lists no injectable stanozolol for people. The best human data for the injection come from a handful of British trials from the 1980s and early 1990s that tested a single 50 mg dose to boost clot-dissolving activity around surgery. Outside medicine it is used by bodybuilders and athletes, and it is banned in sport.

This page summarizes what federal regulations, the former human label, the clinical trials and case reports say about the injectable form. It is for education only and is not medical advice.

Property	Detail
Drug class	17α-methylated anabolic-androgenic steroid (DHT derivative with a fused pyrazole ring)
Form	Injectable suspension, 50 mg stanozolol per mL (no ester)
Route	Deep intramuscular injection
US human approval	None for the injection; the only human application, oral Winstrol tablets (NDA 012885), is discontinued
US veterinary listing	21 CFR 522.2150: dogs, cats and horses; prescription by a veterinarian only
Doses in human trials	Single 50 mg IM injection, usually given the day before surgery
Half-life	No human data; median elimination half-life of 82.1 h in horses after IM injection
Formula	C₂₁H₃₂N₂O, 328.5 g/mol
US schedule	Schedule III controlled substance
WADA status	Prohibited at all times (S1.1 anabolic androgenic steroids), non-Specified

What it is

The injection contains the same molecule as the tablets: stanozolol, formula C₂₁H₃₂N₂O, molecular weight 328.5 g/mol (PubChem). Most injectable steroids, such as testosterone cypionate, are esters dissolved in oil. Stanozolol is instead given as a suspension: the federal listing describes “each milliliter of suspension” as containing 50 mg of stanozolol (21 CFR 522.2150). There is no ester to cleave.

The route changes how the drug enters the body, but not the molecule. Two structural features matter for both forms:

Feature	What it means for the injection
17α-methyl group	Lets the oral form survive the liver. It is still present when the drug is injected, so the class’s liver warnings still apply.
Pyrazole ring fused to the A-ring	Replaces the 3-keto group of testosterone and DHT. Combined with the 5α-reduced skeleton, stanozolol is not expected to convert to estradiol.

The oral page covers stanozolol’s chemistry, metabolism, hereditary angioedema use and the oral trials in more depth. See Winstrol (stanozolol).

Feature	Winstrol tablets	Winstrol Depot
Active ingredient	Stanozolol	Stanozolol
Strength	2 mg tablet	50 mg/mL suspension
Former US human approval	NDA 012885 (approved 1962, discontinued)	None
US veterinary listing	21 CFR 520.2150 (dogs, cats)	21 CFR 522.2150 (dogs, cats, horses)

How it behaves in the body

We found no published study measuring stanozolol blood levels or half-life after an injection in people. The value in the facts table comes from horses.

In horses given 0.55 mg/kg intramuscularly, plasma was sampled for up to 64 days (Soma et al., J Vet Pharmacol Ther 2007):

Parameter (horses, IM)	Value
Median elimination half-life	82.1 h
Mean peak plasma level	4,118.2 pg/mL
Total exposure (AUC)	700.1 ng·h/mL

These figures describe horses and may not carry over to people.

Human trials of the injection give only indirect timing clues. After a single 50 mg injection in 12 healthy men, plasminogen activator activity was raised within 24 hours and stayed raised for a week, while plasminogen stayed raised for three weeks (Small et al., Thromb Res 1982). This shows a biological effect lasting weeks after one dose; it is not a measurement of how long the drug itself stays in the blood.

Regulatory status

Human use (US). Drugs@FDA lists one human stanozolol application, NDA 012885 for Winstrol tablets, now discontinued (Drugs@FDA). No injectable stanozolol for people appears there.
Veterinary use (US). 21 CFR 522.2150 lists a 50 mg/mL injectable suspension “for use as an anabolic steroid treatment.” The sponsor number in the listing corresponds to Zoetis Inc. (21 CFR 510.600). Federal law restricts it to use by or on the order of a licensed veterinarian.
Controlled substance. Stanozolol is named in Schedule III of the US Controlled Substances list, along with its salts, esters and ethers (21 CFR 1308.13).

The veterinary listing sets these conditions of use (21 CFR 522.2150):

Species	Labeled dose	Schedule
Cats and small dogs	25 mg, deep IM in the thigh	Weekly, for several weeks
Larger dogs	50 mg, deep IM in the thigh	Weekly, for several weeks
Horses	25 mg per 100 lb body weight, deep IM in the gluteal region	Weekly, for no more than 4 weeks

The listing adds that it must not be used in horses intended for human consumption.

What the research shows

The human trials of injected stanozolol were run in Glasgow and Nottingham in the 1980s and early 1990s, and the Glasgow studies used a product named Stromba. Their goal was to raise fibrinolysis (the body’s system for dissolving blood clots) around surgery. None measured muscle, strength or performance. We found no randomized trial of injectable stanozolol on body composition in people.

Fibrinolysis and clotting proteins

In the first study, 12 healthy male volunteers each received one 50 mg intramuscular injection (Small et al., Thromb Res 1982):

plasminogen activator rose significantly by 24 hours and stayed raised for one week;
plasminogen rose by day 2 and stayed raised for three weeks;
HDL cholesterol fell, and total and LDL cholesterol rose, when measured one month after the injection.

The same group then gave 14 high-risk surgical patients a single 50 mg injection before surgery and compared them with 13 untreated controls (Blamey et al., Thromb Res 1983). In controls, plasminogen activator activity fell on the first day after surgery, the so-called “fibrinolytic shutdown.” In treated patients it did not fall, and the difference between groups was significant (p under 0.05).

Stanozolol also raised protein C, a natural anticoagulant. In 16 elderly surgical patients, a 50 mg injection the day before surgery raised protein C to 1.11 times its starting level within 24 hours and to 1.19 times seven days after the operation (Kluft et al., Thromb Res 1984). In a separate comparison, the injection shortened the post-surgical fall in protein C (23 patients vs 26 on placebo) but did not prevent clots (Blamey et al., Thromb Haemost 1985).

Prevention of deep vein thrombosis

The lab changes did not translate into fewer clots. A double-blind trial randomized 60 patients having elective abdominal surgery to stanozolol 50 mg or placebo by injection, given 24 hours before surgery (Blamey et al., Thromb Haemost 1984):

Group	Deep vein thrombosis on leg scan
Placebo	11 of 31 (35%)
Stanozolol 50 mg IM	12 of 29 (41%)

Stanozolol did prevent the post-surgical fall in plasminogen activator, as in the earlier study, but clots were no less common. The authors concluded that this regimen does not prevent postoperative deep vein thrombosis.

Arterial bypass surgery

A double-blind trial randomized 27 patients having femoropopliteal (leg artery) bypass to stanozolol or placebo (Berridge et al., Br J Surg 1991). The stanozolol group received 50 mg intramuscularly 24 hours before surgery, then 5 mg by mouth twice daily for 6 weeks.

Despite the injected dose, significant effects on plasminogen, fibrinogen and clot-lysis time did not appear until day 7 after surgery and peaked at 6 weeks.
Early graft thrombosis occurred in 2 placebo patients and 1 stanozolol patient.
Differences in platelet build-up on the graft did not reach statistical significance.

The authors concluded that this approach was “not a practical proposition.”

Side effects and risks

Labeled warnings for stanozolol

The former Winstrol tablet label carried the warnings shared by anabolic steroids (Winstrol label). They concern the drug, not the route:

Peliosis hepatis: blood-filled cysts in the liver, sometimes not found until life-threatening liver failure or abdominal bleeding.
Liver tumors: usually benign, but fatal malignant tumors have been reported.
Blood lipid changes: lower HDL and sometimes higher LDL, changes that “may be very marked.”

The label also states that cholestatic hepatitis and jaundice occur with 17α-alkylated androgens “at relatively low doses,” and that anabolic steroids “have not been shown to enhance athletic ability.”

“Injectable Winstrol is easy on the liver.” This claim assumes that skipping the first pass through the gut and liver removes the liver risk. We found no study comparing liver effects of injected and oral stanozolol. The 17α-methyl group linked to the class’s liver toxicity is part of the molecule whichever way it is given, and severe cholestasis has been reported after injected stanozolol (see below).

Liver

A 19-year-old man injected stanozolol 50 mg intramuscularly every other day for 2 months (Stępień et al., Clin Exp Hepatol 2015). The case report describes:

total bilirubin of 44.34 mg/dL on admission, rising to 56.64 mg/dL, with an INR of 1.7;
only a slight rise in ALT (63 U/L), despite the very high bilirubin;
toxic hepatitis with intrahepatic cholestasis (blocked bile flow inside the liver) and periportal fibrosis on biopsy;
liver tests that returned to normal 5 months after he stopped.

In another report, two amateur bodybuilders who used stanozolol for 6 weeks (the abstract does not state the route) developed bilirubin around 50 mg/dL and bile cast nephropathy, a kidney injury caused by bile pigment. Both needed hemodialysis (Tabatabaee et al., Iran J Kidney Dis 2015).

Cholesterol

Even a single 50 mg injection lowered HDL and raised total and LDL cholesterol one month later in healthy men (Small et al. 1982). The abstract does not give the size of the change. With oral stanozolol, controlled trials found HDL falls of a third or more; see Winstrol (stanozolol).

Injection-site reactions

Several case reports describe local problems after stanozolol injections:

Muscle breakdown. A 39-year-old bodybuilder developed localized rhabdomyolysis (muscle breakdown) of the deltoid on the day he injected stanozolol into it. He was treated with IV fluids, and his pain and movement improved within 4 days without kidney damage (Farkash et al., J Athl Train 2009).
Granulomas. A man who had injected stanozolol into his buttocks for two months developed red, hardened nodules. Biopsy showed a sarcoid-like granulomatous reaction with no infection or foreign material found. The lesions responded to oral prednisolone plus minocycline and healed with pigment changes (Herlekar et al., Indian Dermatol Online J 2026).
Skin necrosis. Embolia cutis medicamentosa (Nicolau syndrome), a rare injection reaction that damages the skin around the injection site, has been reported after intramuscular stanozolol (Al-Wattar-Ceballos and Jiménez-Lara, JEADV 2025).

Hormonal and virilizing effects

The label lists, in men, inhibition of testicular function, testicular atrophy, oligospermia (low sperm count) and impotence. In women it lists clitoral enlargement and menstrual irregularities, and it warns that therapy must be stopped or reduced when mild virilization appears to prevent irreversible change (Winstrol label). These effects come from the drug itself, so they are expected with the injection as well.

Quality and contamination

No human injectable stanozolol is FDA-approved, so product sold for human use in the US comes from outside the regulated drug supply. Analyses of seized anabolic steroids, including stanozolol products, show frequent mislabeling:

Of 70 products confiscated in German house searches, 18 (25.7%) did not contain what the label declared. Fake packaging was often hard to tell from the original (Thevis et al., J Anal Toxicol 2008).
Of 40 seized injectable and capsule steroid samples in Brazil, including stanozolol, 8 lacked the labeled active ingredient. Others contained other substances or less drug than stated, and 4 contained sildenafil (Ribeiro et al., Steroids 2018).

Legal status and use in sport

United States: Schedule III controlled substance (21 CFR 1308.13); approved only as a veterinary drug.
Sport: the WADA 2026 Prohibited List names stanozolol under S1.1 anabolic androgenic steroids. It is prohibited in and out of competition, and all S1 substances are non-Specified (WADA 2026 Prohibited List).

Key takeaways

Same drug, different route. Winstrol Depot is a 50 mg/mL suspension of stanozolol itself, not an ester, and it shares the oral form’s 17α-methyl group.
Veterinary only in the US. Federal regulations list the injection for dogs, cats and horses; no injectable stanozolol has a US human approval.
Little human pharmacokinetic data. No human half-life has been published. In horses the median elimination half-life after injection was about 82 hours.
Human trials tested clotting, not muscle. A single 50 mg injection boosted fibrinolysis for days to weeks, but did not reduce deep vein thrombosis after surgery (41% vs 35% on placebo).
Injection does not make it liver-safe. Severe cholestasis has been reported after injected use, and a single injection lowered HDL.
Local reactions are documented. Case reports describe muscle breakdown, granulomas and skin necrosis at injection sites.

Sources

Food and Drug Administration. Stanozolol (injectable), 21 CFR 522.2150. eCFR.
Food and Drug Administration. Stanozolol (oral), 21 CFR 520.2150; Sponsors of approved applications, 21 CFR 510.600. eCFR 520.2150; eCFR 510.600.
Food and Drug Administration. Drugs@FDA: Winstrol, NDA 012885. FDA.
Winstrol (stanozolol tablets) prescribing information, NDA 012885. RxList.
National Center for Biotechnology Information. Stanozolol, PubChem CID 25249. PubChem.
Soma LR, Uboh CE, Guan F, et al. Pharmacokinetics of boldenone and stanozolol and the results of quantification of anabolic and androgenic steroids in race horses and nonrace horses. J Vet Pharmacol Ther. 2007;30(2):101–108. PubMed.
Small M, McArdle BM, Lowe GD, et al. The effect of intramuscular stanozolol on fibrinolysis and blood lipids. Thromb Res. 1982;28(1):27–36. PubMed.
Blamey SL, McArdle BM, Burns P, et al. Prevention of fibrinolytic shut-down after major surgery by intramuscular stanozolol. Thromb Res. 1983;31(3):451–459. PubMed.
Kluft C, Bertina RM, Preston FE, et al. Protein C, an anticoagulant protein, is increased in healthy volunteers and surgical patients after treatment with stanozolol. Thromb Res. 1984;33(3):297–304. PubMed.
Blamey SL, Lowe GD, Bertina RM, et al. Protein C antigen levels in major abdominal surgery: relationships to deep vein thrombosis, malignancy and treatment with stanozolol. Thromb Haemost. 1985;54(3):622–625. PubMed.
Blamey SL, McArdle BM, Burns P, et al. A double-blind trial of intramuscular stanozolol in the prevention of postoperative deep vein thrombosis following elective abdominal surgery. Thromb Haemost. 1984;51(1):71–74. PubMed.
Berridge DC, Frier M, Westby JC, et al. Double-blind randomized trial of perioperative fibrinolytic enhancement for femoropopliteal bypass. Br J Surg. 1991;78(1):101–104. PubMed.
Stępień PM, Reczko K, Wieczorek A, et al. Severe intrahepatic cholestasis and liver failure after stanozolol usage - case report and review of the literature. Clin Exp Hepatol. 2015;1(1):30–33. PubMed.
Tabatabaee SM, Elahi R, Savaj S. Bile cast nephropathy due to cholestatic jaundice after using stanozolol in 2 amateur bodybuilders. Iran J Kidney Dis. 2015;9(4):331–334. PubMed.
Farkash U, Shabshin N, Pritsch Perry M. Rhabdomyolysis of the deltoid muscle in a bodybuilder using anabolic-androgenic steroids: a case report. J Athl Train. 2009;44(1):98–100. PubMed.
Herlekar R, Singh S, Chatterjee D, Vinay K. Injection site sarcoid-like granulomatous reaction following stanozolol. Indian Dermatol Online J. 2026;17(3):416–418. PMC.
Al-Wattar-Ceballos O, Jiménez-Lara A. Embolia cutis medicamentosa after intramuscular stanozolol injection. J Eur Acad Dermatol Venereol. 2025;39(10):1844–1845. PubMed.
Thevis M, Schrader Y, Thomas A, et al. Analysis of confiscated black market drugs using chromatographic and mass spectrometric approaches. J Anal Toxicol. 2008;32(3):232–240. PubMed.
Ribeiro MVM, Boralle N, Felippe LG, et al. (1)H NMR determination of adulteration of anabolic steroids in seized drugs. Steroids. 2018;138:47–56. PubMed.
Drug Enforcement Administration. Schedule III, 21 CFR 1308.13. eCFR.
World Anti-Doping Agency. Prohibited List 2026. WADA 2026 Prohibited List.

Winstrol Depot (Injectable Stanozolol)