Glucosamine, commonly consumed for the treatment of osteoarthritis, is classified as a nutritional supplement; however, there are few data regarding its metabolic or vascular effects. Glucosamine is a component of the hexosamine pathway, which has been implicated in the development of insulin resistance. Anecdotal reports suggest that glucosamine consumption can increase circulating cholesterol concentrations. To investigate the metabolic and vascular effects of glucosamine supplementation, we studied male and female LDL receptor-deficient mice fed a Western diet (21% fat, 0.15% cholesterol). Three groups of 6-10 mice of each gender received either no supplement, 15 mg . kg(-1) . d(-1) glucosamine (equivalent to an average human dose), or 50 mg . kg(-1) . d(-1) glucosamine added to their drinking water for 5, 10, or 20 wk. Plasma cholesterol and triglyceride concentrations increased in all mice with the addition of the Western diet. However, after 20 wk of treatment, cholesterol and triglyceride concentrations increased further in male mice consuming glucosamine compared with control groups. Glucosamine-supplemented mice had increased initiation of atherosclerosis after 5 wk; however, there was no effect on progression of atherosclerosis in either gender after longer periods of glucosamine supplementation (10 or 20 wk). Although long-term glucosamine supplementation exacerbated the hyperlipidemia in male mice, no increase in atherosclerosis occurred. Thus, glucosamine supplementation appears to be safe, with no adverse vascular consequences.