Using the data of 131 patients with non-insulin dependent diabetes mellitus (NIDDM), the correction formulas of fructosamine value ([FRA]) were devised to standardize the uncorrected [FRA] to serum albumin concentrations ([ALB]) of 4 g/dl, globulin concentrations ([GLB]) of 3 g/dl, and total protein concentrations ([TP]) of 7 g/dl. The following formula was derived for its maximum correlation coefficient (r) between corrected [FRA] ([FRAc]) and fasting blood glucose concentration ([G]); [FRAc] = [FRA] x 33.3/(7.6 [ALB] + [GLB]). In these 131 diabetic patients, r between uncorrected [FRA] and [G] at 2 weeks ago was 0.562. When corrected by [FRA] x 33.3/(7.6 [ALB] + [GLB]), [FRA] x 4/[ALB], [FRA] + 30 (4 - [ALB]), [FRA] + 23 (4 - [ALB]), [FRA] + 30 (7 - [TP]), [FRA] x 7/[TP], and [FRA] x 3/[GLB], r was, respectively, 0.616, 0.612, 0.595, 0.589, 0.582, 0.581 and 0.478. In 24 patients with NIDDM whose [ALB] is either above 4.5 g/dl or below 3.5 g/dl, r between uncorrected [FRA] and [G] was as low as 0.389 without positive correlation. By using our correction formulas of [FRA] x 33.3/(7.6 [ALB] + [GLB]) or [FRA] x 4/[ALB], r was statistically increased, respectively, to 0.769 or 0.788 (P < 0.05 in both cases) in contrast to no significant increase of r by other formulas being at 0.598, 0.556, 0.540, 0.562 and 0.121. Based on these analyses, it is concluded that our correction formula of [FRA] by [FRAc] = [FRA] x 33.3/(7.6 [ALB] + [GLB]) accurately reflects [G] in NIDDM even with hypo- or hyper-albuminemia, and [FRAc] = [FRA] x 4/[ALB] is useful for practical application for its simplicity.