 Metabolic syndrome MS has an increasing prevalence worldwide and there is an urgent need for improvement of medical treatment. In traditional medicine phlebotomy blood letting is a recommended treatment for subjects with obesity and vascular disease. Recent studies showed that blood letting with iron depletion may improve insulin sensitivity in patients with diabetes mellitus. The investigators aimed to test if traditional blood letting has beneficial effects in patients with MS. A randomized trial with a sample size of 64 self-referred MS patients was conducted. Patients in the blood letting group were allocated to blood letting intervention and the control group was offered a later treatment waiting list. In the intervention group 300-400 ml of venous blood were withdrawn at day 1 and after 4 weeks. Primary outcomes were the change of systolic blood pressure and of insulin sensitivity as measured by HOMA-Index. 