What are the recommended laboratory tests and targets for managing diabetes?

Recommended Laboratory Tests and Targets for Managing Diabetes

HbA1c is the cornerstone laboratory test for diabetes management, and should be measured every 3 months until glycemic targets are achieved, then every 6 months for patients with stable control. 1

Core Laboratory Monitoring

HbA1c Testing

Frequency:

• Every 3 months for patients whose therapy has recently changed or who are not meeting glycemic goals 1, 2
• Every 6 months for patients meeting treatment goals with stable glycemic control 1, 3
• Only NGSP-certified methods performed in accredited laboratories should be used 1, 2

Target Levels:

• Standard target: <7% (<53 mmol/mol) for most nonpregnant adults with diabetes 1, 3, 4
• More stringent target: <6.5% for selected individuals with short diabetes duration, long life expectancy, no significant cardiovascular disease, if achievable without significant hypoglycemia 1, 4
• Less stringent target: <8% for patients with history of severe hypoglycemia, limited life expectancy, extensive comorbidities, or advanced complications 1, 2, 4

Critical caveat: HbA1c may be unreliable in conditions affecting red blood cell turnover (hemoglobin variants, hemolytic anemia, severe anemia), requiring alternative markers like fructosamine or reliance on plasma glucose criteria 1, 2

Blood Glucose Monitoring

Self-Monitoring of Blood Glucose (SMBG):

• Patients on multiple daily insulin injections should perform SMBG at least 4 times daily 1
• Patients taking insulin or medications with hypoglycemia risk should perform finger-stick monitoring 3
• Preprandial target: 80-130 mg/dL 4
• Peak postprandial target: <180 mg/dL (measured 1-2 hours after beginning of meal) 4

Continuous Glucose Monitoring (CGM):

• Real-time CGM should be used in conjunction with insulin for teens and adults with type 1 diabetes not meeting glycemic targets or with hypoglycemia unawareness 1
• Consider CGM for type 2 diabetes patients with unexplained severe hypoglycemia, hypoglycemia unawareness, or refractory hyperglycemia 3

Additional Essential Laboratory Tests

Kidney Function Monitoring

Urine Albumin-to-Creatinine Ratio:

• Annual testing starting 5 years after type 1 diabetes diagnosis in pubertal or post-pubertal individuals 2
• Use morning spot urine samples 2
• Increase frequency to every 6 months if eGFR <60 mL/min/1.73 m² and/or albuminuria >30 mg/g creatinine 2

Ketone Testing

When to Test:

• Individuals prone to ketosis (type 1 diabetes, history of DKA, or on SGLT2 inhibitors) should measure ketones with unexplained hyperglycemia or symptoms of ketosis 1
• β-hydroxybutyrate in blood is the preferred method for diagnosis and monitoring of DKA 1
• Blood ketone determinations using nitroprusside reaction should NOT be used to monitor DKA treatment 1

Lipid Profile

• Regular lipid monitoring is essential for cardiovascular risk assessment 4

Additional Screening

• Thyroid function tests and celiac disease screening should be considered periodically in type 1 diabetes due to increased autoimmune disease prevalence 2

Special Populations

Gestational Diabetes

Screening:

• All pregnant women with risk factors should be tested at first prenatal visit 1
• All pregnant women without known diabetes should be screened at 24-28 weeks gestation 1

Targets during pregnancy:

• Fasting plasma glucose: <95 mg/dL (<5.3 mmol/L) 1
• 1-hour postprandial: <140 mg/dL (<7.8 mmol/L) OR 2-hour postprandial: <120 mg/dL (<6.7 mmol/L) 1
• Women with pre-existing diabetes should aim for HbA1c <6.0% (<42 mmol/mol) during pregnancy 1

Postpartum follow-up:

• Test for prediabetes or diabetes 4-12 weeks postpartum using oral glucose tolerance test 1
• Lifelong screening at least every 3 years for women with history of GDM 1

Tests NOT Recommended

• Urine glucose testing is not recommended for routine diabetes care 1

Point-of-Care Testing Considerations

• Point-of-care HbA1c testing should be restricted to FDA-approved devices at CLIA-certified laboratories performing moderate complexity testing or higher 1, 2
• While convenient for timely treatment changes, proper certification is essential 1, 2