Fasting intermediary metabolite concentrations were measured in comparable groups of women either in the follicular or luteal phase of the menstrual cycle or taking low-dose estrogen combined oral contraceptive preparations. Blood total ketone bodies concentrations were significantly elevated in oral contraceptive users (p less than 0.05 v follicular and luteal groups) whilst blood alanine levels were lower (p less than 0.01 v follicular).