In normal human plasma the concentrations of the renal osmolyte, glyci
ne betaine, are usually between 20 and 70 mu mol/l, in adult males (me
dian 44 mu mol/l) higher than in females 34 mu mol/l). Concentrations
are lower in renal disease (median 28 mu mol/l) and normal in diabetes
. Urinary excretion of glycine betaine shows no sex difference and is
frequently elevated both in renal disease and in diabetes (medians: no
rmal, 6.2, renal 12.3 and diabetes, 39.7 mmol/mol creatinine). The ele
vation in diabetes does not strongly correlate with known renal diseas
e, nor with either urinary microalbumin or plasma creatinine. There is
no correlation with glycated haemoglobin. The positive correlation wi
th the excretions of another renal osmolyte, sorbitol, was highly sign
ificant in diabetic subjects. In the diabetic group there was also a s
ignificant negative correlation between plasma glycine betaine and uri
ne microalbumin.