BCG therapy is well tolerated by the majority of patients who receive it. It is, however, a live bacteria, and thus has a small potential of causing infection. Approximately 75% of the patients do complain of frequency and urgency immediately after the treatment, although this usually resolves quickly.
Approximately 10% of people complain of some pain, which also quickly resolves. Twenty percent of patients will acquire a urinary tract infection unrelated to the BCG bacteria; this can usually be easily treated with a short course of antibiotics. Thirty percent of patients will have some bleeding after the treatment. About 25% of patients will experience mild flu-like symptoms of fever and achiness. The good news is that these side effects are usually short-lived and mild; thus, only 5% to 10% of patients will be bothered by the side effects enough to discontinue the treatment.
Symptoms such as a low-grade fever, chills, a flu-like malaise, and occasional joint aches are signs that the body is responding appropriately to BCG. If these symptoms are more than mild, they can also be a sign of serious infection by BCG. Fevers of more than 101.5°F, especially those that begin after 24 hours, persist more than 48 hours, or occur in the early evening, are more indicative of BCG infection. Patients suspected of having infection by BCG will usually be admitted to the hospital and treated with three antibiotics.
Those who do not respond quickly may also be treated with steroids.
Approximately 1% will develop an inflammation of the prostate called prostatitis. This is usually treated with nonsteroidal anti-inflammatory medications such as ibuprofen, delaying treatments by 1 to 2 weeks, shortening the cycle of treatments, or antibiotics.