Depo-Testosterone is a brand-name injectable form of testosterone used to treat low testosterone in men. It contains testosterone cypionate, a modified version of the hormone that dissolves in oil and releases slowly into the body after being injected into a muscle. The medication is a Schedule III controlled substance, meaning it requires a prescription and is regulated due to its potential for misuse.
How Depo-Testosterone Works
The active ingredient, testosterone cypionate, is testosterone with a chemical attachment that makes it dissolve in oil rather than water. Each vial contains the hormone suspended in cottonseed oil, with benzyl alcohol added as a preservative. When injected into a muscle (typically the thigh or buttock), the oil creates a depot, or reservoir, that gradually releases testosterone into the bloodstream over days.
The half-life of testosterone cypionate is approximately eight days, which means your body takes about a week to use up half of each dose. This slow release is what allows injections to be spaced two to four weeks apart rather than given daily. Testosterone levels peak within the first few days after injection, then steadily decline until the next one.
What It Treats
Depo-Testosterone is FDA-approved for testosterone replacement in men whose bodies don’t produce enough of the hormone on their own. This includes two main categories: problems originating in the testes themselves (from injury, infection, or genetic conditions) and problems originating in the brain’s signaling system that tells the testes to produce testosterone (caused by tumors, radiation, or other conditions affecting the pituitary gland).
It is not approved for age-related testosterone decline alone, though it is sometimes prescribed for this purpose. The medication suppresses sperm production, so it is not appropriate for men actively trying to conceive.
Typical Dosing and Injection Process
The standard dose ranges from 50 to 400 mg, injected into a muscle every two to four weeks. Your prescriber will typically start at a lower dose and adjust based on blood work. Many people on stable therapy settle into a routine of injecting every one to two weeks at a lower per-injection dose, which helps keep testosterone levels more consistent and reduces the peaks and valleys that come with longer intervals.
Injections go into the thigh muscle (vastus lateralis) or the upper outer area of the buttock (gluteus). Because the oil is thick, a larger-bore needle is often used to draw the medication into the syringe, then swapped for a smaller needle (typically 23-gauge, about 1 inch long) for the actual injection. Some people administer injections at home after being trained by a healthcare provider, while others go to a clinic for each dose.
Blood Work and Monitoring
Starting Depo-Testosterone means committing to regular blood tests. Current guidelines recommend checking testosterone levels, red blood cell counts (hemoglobin and hematocrit), and prostate-specific antigen (PSA) at 3 to 6 months after starting therapy, then again at 12 months. After the first year, PSA is checked annually.
Timing matters for accurate results. If you inject every week, blood should be drawn on day 3 or 4 after your injection, midway between doses. This avoids catching levels at their highest peak or lowest trough, giving a more realistic picture of your average testosterone level. Doses are adjusted if total testosterone exceeds 900 ng/dL or falls below the normal range.
Side Effects and Risks
The most common medical concern with testosterone therapy is an increase in red blood cell production. Your body responds to higher testosterone by making more red blood cells, which thickens the blood and can raise the risk of blood clots. Studies have found that rates of elevated red blood cell counts (a condition called erythrocytosis) can be surprisingly high, reaching up to 66.7% in some groups of men on testosterone. Up to 2.7% of men on testosterone therapy develop blood clots.
This is why hematocrit monitoring is non-negotiable. If your hematocrit (the percentage of your blood made up of red blood cells) rises above 50 to 51%, your dose will likely be reduced. If it exceeds 54%, treatment is typically paused until levels normalize. Some providers recommend blood donation or therapeutic phlebotomy (having blood drawn to lower the count) for persistently elevated levels.
Other common side effects include acne, oily skin, changes in mood or libido, hair thinning, and fluid retention. Testosterone also suppresses the body’s natural hormone production, which shrinks the testes over time and significantly reduces sperm count.
Who Should Not Use It
Depo-Testosterone is contraindicated in men with breast cancer, prostate cancer, or a PSA level above 4 ng/mL (until a urologist has ruled out prostate issues). Men with a hematocrit already above 54% should not start therapy until that is addressed.
Several conditions require careful consideration before starting. Uncontrolled heart failure, untreated obstructive sleep apnea, and severe urinary symptoms from an enlarged prostate all increase the risks of treatment. Because testosterone crosses the placenta, it should never be used during pregnancy. The cottonseed oil base can also cause reactions in people with cottonseed allergies, though this is uncommon.
How It Compares to Other Forms
Testosterone cypionate in Depo-Testosterone is one of several delivery methods for testosterone replacement. Gels and patches provide daily dosing with more stable blood levels but require careful skin-to-skin contact precautions. Pellets implanted under the skin last several months but require a minor office procedure. Nasal gels are applied two or three times daily.
The injectable form remains popular because it is relatively inexpensive, requires attention only every one to four weeks, and delivers reliable absorption. The main trade-off is the fluctuation in testosterone levels between injections, which some people notice as shifts in energy, mood, or libido in the days before their next dose. Shorter injection intervals (weekly rather than biweekly) help flatten this cycle.