Because it is the body's own hormone that is used, which has only been modified to slow down its breakdown, the side effects are few and mild. In the larger studies that have been conducted, the side effects are relatively similar between  test groups taking placebo and test groups taking medicine. Side effects are most common at the beginning of treatment, which is why the initial dose is low and increased slowly.

You may experience nausea, gas, and diarrhoea, mild gastritis, or constipation, but with the support of a dietitian, most symptoms can usually be avoided.