What blood tests are recommended for diabetes monitoring?

Blood Tests for Diabetes Monitoring

For ongoing diabetes monitoring, measure HbA1c every 3 months until glycemic targets are achieved, then at least every 6 months, along with annual urine albumin-to-creatinine ratio testing and periodic fasting plasma glucose measurements. 1, 2

Core Laboratory Tests

Hemoglobin A1c (HbA1c)

• HbA1c is the primary test for assessing long-term glycemic control, reflecting average glucose levels over the preceding 60-90 days 1, 2, 3
• Measure HbA1c every 3 months until acceptable glycemic targets are reached, then at least every 6 months for patients meeting treatment goals 1, 2
• For patients not meeting glycemic goals or with recent treatment changes, continue quarterly testing 2
• Only use NGSP-certified methods in accredited laboratories to ensure accuracy 1, 3
• Target HbA1c <7% for most adults with diabetes, though more stringent targets (<6.5%) may be appropriate for selected patients with short disease duration, no cardiovascular disease, and long life expectancy 3

Fasting Plasma Glucose (FPG)

• Measure FPG periodically to supplement HbA1c monitoring, particularly when adjusting oral glucose-lowering medications in patients not taking insulin 4, 1
• Collect samples after at least 8 hours of fasting in tubes containing citrate buffer, or place immediately in ice-water slurry and centrifuge within 15-30 minutes to minimize glycolysis 1, 2
• FPG provides immediate assessment of current glycemic status, complementing the longer-term picture from HbA1c 4

Urine Albumin-to-Creatinine Ratio (uACR)

• Measure uACR annually in all adults with diabetes using first morning void spot urine samples to screen for diabetic kidney disease 1, 2
• First morning samples are preferred to minimize variability 1
• Increase testing frequency to every 6 months if estimated glomerular filtration rate is <60 mL/min/1.73 m² and/or albuminuria is >30 mg/g creatinine 1, 2

Additional Testing Based on Clinical Context

Lipid Profile

• Measure lipid panel to assess cardiovascular risk factors, particularly in patients with hypertension, low HDL cholesterol, or elevated triglycerides 2
• This is critical since cardiovascular disease is the leading cause of mortality in diabetes 4

C-Peptide

• Consider measuring C-peptide to distinguish type 1 from type 2 diabetes in ambiguous cases, such as individuals with type 2 phenotype who present in ketoacidosis 1, 2
• For insulin pump therapy coverage, measure fasting C-peptide when simultaneous fasting plasma glucose is <220 mg/dL 1

Blood Ketones

• Use blood ketone determinations for diagnosis of diabetic ketoacidosis and monitoring during treatment 2
• Recommend testing for individuals prone to ketosis when they have unexplained hyperglycemia or symptoms of ketosis 2

Critical Caveats and Pitfalls

HbA1c Limitations

• HbA1c may not be reliable in conditions affecting red blood cell turnover, including sickle cell disease, pregnancy, hemodialysis, recent blood loss or transfusion, hemolytic anemia, aplastic anemia, and erythropoietin therapy 2, 5
• In these situations, use only plasma glucose criteria for diagnosis and monitoring 2
• HbA1c does not provide information about glycemic variability or hypoglycemia, which are important management factors 2

Quality Assurance Requirements

• HbA1c testing must use NGSP-certified methods with analytical performance meeting strict standards 1
• Point-of-care A1C testing should be restricted to FDA-approved devices at CLIA-certified laboratories performing moderate complexity testing or higher 2
• Glucose measurement should have analytical imprecision ≤2.4%, bias ≤2.1%, and total error ≤6.1% 1
• For urine albumin measurement, between-day precision should be ≤6%, bias ≤7% to 13%, and total allowable error ≤24% to 30% 1

Self-Monitoring Integration

• While laboratory testing provides the foundation for monitoring, patient self-monitoring of blood glucose remains essential for day-to-day management and detecting immediate glycemic excursions 4, 2
• Compare patient self-testing results with simultaneous laboratory testing periodically to verify accuracy of home monitoring 4

Monitoring Frequency Summary

Standard monitoring schedule:

• HbA1c: Every 3 months until targets met, then every 6 months 1, 2
• uACR: Annually (every 6 months if kidney disease present) 1, 2
• FPG: Periodically as clinically indicated 1
• Lipid profile: As indicated for cardiovascular risk assessment 2