A 34-year-old female patient developed chronic renal failure due to malignant hypertension. She has been on hemodialysis for 10 years. Her past medical records were remarkable for 20 random blood transfusions, but no history of diabetes or other medical diseases. She has been anuric for 9 years. A high panel reactive antibody and a repeated positive B and T-CDC-AGH crossmatch with her ABO-compatible sister were detected. She was then enrolled in a desensitization protocol in order to receive her sister’s kidney. The protocol consisted of three monthly intravenous courses of polivalent immunoglobulin, 1 g/kg/day for 2 consecutive days. She received two 8-hour infusions in 2 consecutive months with no adverse events. The third treatment was initiated after an uneventful dialysis session and was performed in 8 hours. Twelve hours after the infusion procedure, she complained of mouth dryness and appeared dehydrated. A glucose determination by a common device (Accucheck, Roche Diagnostics, Mannheim, Germany) yielded a high value (>400 mg/dl). Repeated determinations again revealed elevated values and the patient was strongly symptomatic. Diabetes mellitus and hyperosmolarity state were suspected and she received a total of 20 intravenous and 30 subcutaneous units of regular insulin and saline solution. Then she presented tetany, for which calcium plus magnesium solutions were infused. The contractions ceased but she remained sweaty and at low consciousness. Fifty milliliters of a 50% glucose solution were infused and the patient recovered to normal sensory level. Low glucose (34 mg/dl) and ionic calcium and magnesium concentrations (4.5 and 1.8 mg/dl, respectively) were observed. After careful review, it was observed that a maltose-containing immunoglobulin solution (Octagan, MSD, Minneapolis, MN) was used instead of the usual glucose-containing solution (Endobulin, Baxter AG, Vienna, Austria). The device uses the principle of bioamperometry, by which glucose dehydrogenase in a strip converts the glucose in the blood sample to gluconolactone. This reaction creates a harmless electrical current that is interpreted by the meter as blood sugar. However, the test may be affected by many variables such as high bilirubin, triglyceride, acetaminophen, and uric acid values, as well as galactose and maltose blood levels greater than 10 and 16 mg/dl, respectively, creating a false high value. In peritoneal dialysis, the use of icodextrin solutions is another example of this kind of misinterpretation. Icodextrin is a high-molecular weight glucose polymer that induces transcapillary ultrafiltration by “colloid” osmosis. Its median value of absorption is 40% and it is hydrolyzed in the plasma by α-amylases into smaller glucose polymers, especially maltose, maltotriose and maltotetrose. These oligosaccharides are further metabolized by tissue maltases into glucose. Indeed, the interference with glucose-monitoring systems that employ glucose oxidase or hexokinase methods in PD patients was previously described. The widespread use of the polivalent immunoglobulins in clinical practice, and the large formulation variety of these products in the international market, should alert the internist and mainly the nephrologist for this trivial but potentially serious misinterpretation. Sérgio P. Souza Nephrology Department Hospital das Clinicas da Universidade de São Paulo São Paulo, Brazil Maria Cristina R. Castro Renal Transplantation Unit Urology Department Hospital das Clinicas da Universidade de São Paulo São Paulo, Brazil Rodrígo A. Rodrigues Nephrology Department Hospital das Clinicas da Universidade de São Paulo São Paulo, Brazil Rogérío H. Passos Nephrology Department Hospital das Clinicas da Universidade de São Paulo São Paulo, Brazil Luiz E. Ianhez Renal Transplantation Unit Urology Department Hospital das Clinicas da Universidade de São Paulo São Paulo, Brazil