The 24-hour urinary creatinine excretion value can be used as an index of protein nutrition; the creatinine height index and lean body mass can be estimated from this value. On the basis of longitudinally measured 24-hour urinary creatinine excretions during the initial 7 years of type 1 diabetes in an incidence cohort of 147 adult patients, we studied creatinine height index and lean body mass and possible relationships to sequential measurements of glycated hemoglobin (HbA1c). The patients were divided into four groups according to their glycemic control during these 7 years: I, HbA1c < 7.4% (n = 37); II, HbA1c 7.4% to 8.2% (n = 37); III, HbA1c 8.3% to 8.9% (n = 38); IV, HbA1c > 8.9% (n = 35). One year after the onset of diabetes, height indices were as follows (% of normal values, median and quartiles): I, 104% (90 to 116); II, 101% (78 to 105); III, 121% (92 to 128); IV, 87% (78 to 109) ([IV] < [I to III]; p < .05). During the following 6 years no significant differences in height index were observed among the four groups of patients at any point in time. Slightly higher calculated lean body mass values were found in the most well-controlled patients, but otherwise no differences were found in lean body mass. It is concluded that, apart from the first year, indices of protein nutrition remain normal during the initial 7 years of type 1 diabetes, even in patients with poor glycemic control.