The present invention provides methods for using human placental alkaline phosphatase or an active derivative to reduce blood glucose level in a mammal. Treatment regimens provided by the invention maybe used to control Type 1 and Type 2 forms of diabetes in humans. The methods and treatment regimens maybe effective to maintain the human's blood glucose level below about 10 mM, and preferably within the normal range of 4 mM to 7 mM. The methods and treatment regimens may be used in combination with administration of known anti-diabetic medicaments. Also provided by the invention is a method for inducing weight loss or reducing an expected weight gain caused by or associated with obesity or Type 2 diabetes. The invention further provides a preparation for administration to a human, the preparation comprising homogeneous purified human placental alkaline phosphatase in a physiologically acceptable carrier.