Short answer: The Testopel label lists side effects reported after approval without giving percentages: implant site infection and pellets pushing out of the skin, breast enlargement, frequent or long erections, acne, male-pattern hair loss, fluid retention, nausea, a rise in red blood cells, headache and mood changes. Its warnings cover blood clots, blood pressure, heart risk, liver tumors with long high-dose use and abuse. It has no boxed warning.
What Testopel is approved for: Testopel is approved as testosterone replacement in males with low or absent natural testosterone due to primary hypogonadism (testicular failure) or hypogonadotropic hypogonadism (a pituitary or hypothalamus cause). It may also be used to start puberty in carefully selected boys with clearly delayed puberty. The label says safety and effectiveness in men with age-related ("late-onset") hypogonadism have not been established (Indications and Usage).
Source
TESTOPEL (testosterone pellets) for subcutaneous implantation, prescribing information. Endo. DailyMed, version published July 24, 2025. DailyMed setid 03b9c0b1-5884-11e4-8ed6-0800200c9a66
No. The current Testopel label has no boxed warning.
These are the label's own numbers from the Adverse Reactions section. Where the label compares with placebo (a dummy treatment), both columns are shown, so you can see how much more often a reaction happened on Testopel.
| Body system | Reactions the label lists |
|---|---|
| Implantation site | Implantation site infection and pellet extrusion (see Warnings). |
| Endocrine and urogenital, male | Gynecomastia and excessive frequency and duration of penile erections. Oligospermia may occur at high dosages. |
| Skin and appendages | Hirsutism, male pattern of baldness, and acne. |
| Cardiovascular disorders | Myocardial infarction, stroke. |
| Fluid and electrolyte disturbances | Retention of sodium, chloride, water, potassium, calcium and inorganic phosphates. |
| Gastrointestinal | Nausea, cholestatic jaundice, alterations in liver function tests, rarely hepatocellular neoplasms and peliosis hepatis. |
| Hematologic | Suppression of clotting factors II, V, VII, and X, bleeding in patients on concomitant anticoagulant therapy, and polycythemia. |
| Nervous system | Increased or decreased libido, headache, anxiety, depression, and generalized paresthesia. |
| Metabolic | Increased serum cholesterol. |
| Vascular disorders | Venous thromboembolism. |
| Miscellaneous | Rarely anaphylactoid reactions. |
The label says these were identified during post-approval use of testosterone replacement, including Testopel. They are reported voluntarily, so frequency cannot be reliably estimated. No percentages or placebo comparison are given.
Implant site infection (cellulitis and abscess) and pellet extrusion have been reported after insertion. Most reported cases happened within the first month after implantation, though they can happen at any time.
In plasma, testosterone is 98 percent bound to sex-hormone binding globulin and about 2 percent is free.
About one-third of the pellet material is absorbed in the first month, one-fourth in the second month and one-sixth in the third month. The effect usually lasts three to four months, sometimes as long as six months.
Hemoglobin and hematocrit are checked periodically for polycythemia (too many red blood cells) in patients on high doses of androgens, and liver function tests are obtained periodically.
The Warnings and Precautions part of the label lists these. Each line gives the label's heading and what it means in plain words.
Who should not use it. Men with breast cancer or known or suspected prostate cancer. Androgens given in pregnancy can masculinize a female fetus.
Implant site infection and pellet extrusion. Infection (cellulitis and abscess) and pellets pushing out at or near the implant site have been reported, with signs such as hardening, inflammation, bleeding, bruising, drainage, pain and itching. Most cases were in the first month, and some needed further treatment.
Blood clots. Deep vein thrombosis and pulmonary embolism have been reported with testosterone products, including Testopel. Leg pain, swelling, warmth or redness, or sudden shortness of breath are checked for clots, and treatment is stopped if one is suspected.
Heart risk and blood pressure. Long-term heart outcome trials have not been done, and studies of heart attack, stroke and heart-related death are inconclusive. Testosterone can raise blood pressure; it is checked periodically, and testosterone is not recommended with uncontrolled high blood pressure.
Liver and prostate. Long use of high androgen doses has been linked to peliosis hepatis and liver tumors, including liver cancer. Men on androgens may have a higher risk of prostate enlargement and prostate cancer.
Calcium, fluid and breasts. In breast cancer, androgens may raise calcium and are then stopped. Swelling, with or without heart failure, can be serious in people with heart, kidney or liver disease. Breast enlargement often develops and sometimes persists.
Abuse and teen growth. Testosterone has been abused at high doses, which can cause serious heart and mental health problems. In delayed puberty, androgens can speed bone maturation and reduce final height, so bone age is checked every 6 months.
Hard to adjust once implanted. Pellets are much less flexible for dose changes than pills or injections, so the amount is estimated with great care. If testosterone has to be stopped because of a complication, the pellets would have to be removed.
From the Precautions, Information for the Patient that comes with Testopel:
Dose Track has a side-effect log. Each entry records the symptom, a severity (none, mild, moderate, severe or life-threatening), the date and an optional note, and can be tied to a specific dose or logged on its own. The history screen shows what you logged over time, which makes it easier to tell your prescriber when a reaction started and whether it is easing. The app records what you enter; it does not judge whether a symptom is serious. For anything on the label's call-your-doctor list, call your doctor.
This page is what the FDA label says, in plain words. It is not medical advice. Follow your prescriber, and ask them or your pharmacist about anything here.