Mains water is normally chlorinated, and whilst relatively safe may cause mild abdominal upsets. Bottled water is available. Milk is pasteurised and dairy products are safe for consumption. Local meat, poultry, seafood, fruit and vegetables are generally considered safe to eat. There is, however, a risk of biointoxication from raw or cooked fish or shellfish.

Hepatitis B and tuberculosis occur; vaccination is sometimes advised. Dengue fever and Japanese encephalitis can occur in epidemics. Jellyfish might also pose some threat.

Health insurance is strongly advised, owing to the high cost of health care. There is one civilian hospital, the Guam Memorial Hospital, and a number of private clinics, as well as some medical facilities run for US military personnel.