Yes prescribed medicine can cause major side effects. These are usually listed in the information sheet that comes with the prescribed medicine, so check there first. I'll give you an example from experience:
About 2 years ago my doctor decided (against my wishes) to change my medication to a "cheaper" alternative. Within two days I'd developed every single side effect listed on the information sheet, including a grossly swollen left breast. The doctor only agreed to change me back to my original medication, and thought my breast would get better of its own accord.
Well it didn't. I went back the day after and saw the practice nurse for help on managing the pain. She called the doctor in, gave him a severe ticking off, and he put me on two doses of anti-biotics and sent me up to the hospital for tests. Apparently the symptoms mimic a severe form of breast cancer, and they wanted to be sure it wasn't. So 4 mammograms, 3 core biopsies and 2 ultrasounds later, I was told I had a benign breast lump and it would never go away completely. So much for "saving the NHS money".
It has been said that 30% of patients in hospital are there because of the side-effects of the drugs they were originally prescribed.