forteo is a prescription medication used totreat both men and postmenopausal women with osteoporosis who are at high risk for havingbroken bones. forteo is a synthetic hormone that is similar to the one the body makesnaturally (parathyroid hormone). it works by causing the body to build new bone andincrease bone strength by regulating calcium and phosphate. forteo comes in an injectable form that isgiven once daily. it is injected just under the skin of the stomach area or thigh. common side effects include nausea, jointaches, and pain.