Carnitine is an essential factor for the transport of long-chain fatty acids and is important for the heart muscle. A longitudinal study in type 2 diabetic patients was carried out. Carnitine levels were observed before and during metabolic intervention with dietary measures and either sulfonylurea or insulin treatment. In both treatment groups a significant glycemic improvement was observed after 3 months (insulin treatment group: hemoglobin A1c 11.3 +/- 2.8 versus 7.0 +/- 1.0; sulfonylurea treatment group; hemoglobin A1c 11.3 +/- 1.4 versus 7.3 +/- 0.9). Carnitine levels did not differ from a control group and did not change significantly during the observed period.