To evaluate the role of fructosamine/albumin ratio as an alternative screening parameter for gestational diabetes mellitus (GDM), serum fructosamine, albumin, protein, fructosamine/albumin ratio, and oral glucose tolerance were measured in 56 non-pregnant control healthy subjects, and in 96 pregnant women who screened positive after a 50 g glucose challenge-test. Oral glucose tolerance test (OGTT) identified 12 of 96 pregnant women as having GDM. Fructosamine concentration of 1.98 +/- 0.32 mmol/L (mean +/- SD) and fructosamine/albumin ratio of 47 +/- 10 mumol/g (mean +/- SD) has been obtained in nonpregnant control subjects. During the second trimester a lower fructosamine level (1.84 +/- 0.29 mmol/L, p < 0.05) and a higher fructosamine/albumin ratio (62 +/- 15 mumol/g, p < 0.001) occurs in pregnant women, when compared to non-pregnant healthy control subjects, most likely due to the low serum albumin concentration (30 +/- 6 g/L). The serum fructosamine levels and fructosamine/albumin ratio were only slightly higher in the pregnant women with GDM than in normal pregnant women (2.05 +/- 0.47 mmol/L versus 1.84 +/- 0.29 mmol/L, 67 +/- 16 mumol/g versus 62 +/- 15 mumol/g, respectively) but the differences were not statistically significant. The fructosamine and fructosamine/albumin ratio values for normal and GDM groups overlapped considerably. Sensitivity, specificity, positive predictive and negative predictive values for fructosamine were 41.7%, 85.7%, 29.4% and 91%, and for fructosamine/albumin ratio 25%, 79.8%, 15% and 88% respectively. This suggests that both fructosamine and fructosamine/albumin ratio have low sensitivity as predictors of GDM and can therefore not be used as screening tests.