Some side effects of the prolactin test include continuous bleeding and bruising after taking the test, according to WebMD. Following the test, a patient can also experience a swollen vein after removal of blood. The prolactin test examines the levels of the hormone prolactin in the body and is useful in several cases, including determining causes of infertility and erectile dysfunction, halting of menstruation, and identifying extremely low levels of testosterone.
The procedure for the prolactin test involves an elastic band wrapped tightly around the patient's arm and a needle to withdraw blood, explains WebMD. This wrapping can cause the arm to feel tight, while the administration of the needle feels like a slight pinch or does not evoke a feeling at all. The injected area requires the application of pressure for several minutes to lower the chances of bruising. Patients should also advise their doctors if they take any medications that can thin their blood, such as aspirin or warfarin, to prevent the chance of bleeding after the withdrawal of blood. It is rare that a vein becomes swollen after taking a prolactin test, but if it does occur, it is treatable by using a thermal compression each day and applying pressure several times.