Nebido (testosterone undecanoate) 1000mg/4ml injection is a long-acting injectable testosterone formulation primarily indicated for testosterone replacement therapy in men with hypogonadism. However, it may also be used off-label in gender-affirming care for transgender men (assigned female at birth) to masculinise secondary sexual characteristics. Here are potential unwanted/adverse/side effects of Nebido in the context of gender-affirming care:
| Side Effect | Description |
| Acne | Testosterone therapy, including Nebido, may increase oil production in the skin, leading to acne or exacerbating existing acne. |
| Increased body hair growth | One of the desired effects of testosterone therapy in transgender men is increased body hair growth. However, excessive hair growth or unwanted hair growth in certain areas may occur. |
| Male pattern baldness | Testosterone therapy can accelerate male pattern baldness in individuals who are genetically predisposed to it. |
| Voice deepening | Testosterone therapy may cause voice deepening in transgender men due to vocal cord thickening. |
| Clitoral enlargement | Testosterone therapy may lead to clitoral enlargement in transgender men due to tissue growth in the clitoral region. |
| Menstrual changes | Testosterone therapy typically leads to cessation of menstruation (amenorrhea) in transgender men, but irregular bleeding or spotting may occur during the initial stages of treatment. |
| Emotional changes | Some individuals may experience emotional changes, such as increased aggression or irritability, while taking testosterone therapy. |
| Weight gain or redistribution | Testosterone therapy may lead to changes in fat distribution, with increased muscle mass and decreased fat in certain areas. |
| Increased libido | Testosterone therapy often increases libido (sex drive) in transgender men. |
| Mood changes | Testosterone therapy may lead to mood changes, including mood swings, increased energy levels, or changes in emotional well-being. |
| Fluid retention | Testosterone therapy may lead to fluid retention, causing swelling or bloating in the hands, feet, or other parts of the body. |
| Changes in cholesterol levels | Testosterone therapy may affect cholesterol levels, leading to increases in LDL cholesterol (“bad” cholesterol) and decreases in HDL cholesterol (“good” cholesterol). |