What are the recommended ongoing laboratory tests for managing type 1 diabetes?

Ongoing Laboratory Monitoring for Type 1 Diabetes

For patients with type 1 diabetes, measure HbA1c every 3 months until glycemic targets are achieved, then reduce to every 6 months for those with stable control, and perform annual urine albumin-to-creatinine ratio testing starting 5 years after diagnosis in pubertal/post-pubertal individuals. 1

HbA1c Monitoring Schedule

The cornerstone of laboratory monitoring in type 1 diabetes is serial HbA1c measurement, which reflects average glycemia over approximately 2-3 months 1:

• Every 3 months (quarterly): For patients whose therapy has recently changed or who are not meeting glycemic goals 1
• Every 6 months (twice yearly): For patients with stable glycemic control who are meeting treatment goals 1

This testing frequency is supported by evidence showing that quarterly HbA1c measurements for one year are associated with significant reductions in HbA1c values in people with type 1 diabetes 1. Only use NGSP-certified methods performed in accredited laboratories 1, 2.

Target HbA1c Levels

• Standard target: <7% (<53 mmol/mol) for most nonpregnant adults with type 1 diabetes 1
• 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
• Less stringent target: <8% for those with history of severe hypoglycemia, limited life expectancy, extensive comorbidities, or advanced complications 1

Urine Albumin Screening

Annual urine albumin-to-creatinine ratio (uACR) testing is mandatory starting 5 years after type 1 diabetes diagnosis in pubertal or post-pubertal individuals 1, 2:

• Use morning spot urine samples 1, 2
• Increase testing frequency to every 6 months if eGFR <60 mL/min/1.73 m² and/or albuminuria >30 mg/g creatinine 2

This screening detects diabetic kidney disease early, when interventions can slow progression.

Important Caveats and Pitfalls

When HbA1c May Be Unreliable

HbA1c is an indirect measure and can be inaccurate in several conditions 1, 2, 3:

• Hemoglobin variants (sickle cell disease, thalassemia)
• Conditions affecting red blood cell turnover: pregnancy, hemodialysis, recent blood loss or transfusion, erythropoietin therapy
• Anemia or hemolytic conditions

In these situations, use only plasma glucose criteria for diagnosis and monitoring, or consider alternative markers like fructosamine or glycated albumin 1, 2, 3.

HbA1c Limitations in Type 1 Diabetes

Critical point: HbA1c does not measure glycemic variability or hypoglycemia, both crucial in type 1 diabetes management 1, 4. For patients with type 1 diabetes, glycemic control is best evaluated using the combination of HbA1c, continuous glucose monitoring (CGM), and/or self-monitoring of blood glucose 1.

When HbA1c results don't correlate with glucose monitoring data, consider:

• Measurement variability
• Conditions affecting red blood cell lifespan
• Significant glycemic variability with extremes being missed by monitoring 1

Complementary Monitoring (Not Laboratory Tests)

While not laboratory tests per se, these are essential for comprehensive monitoring in type 1 diabetes:

• CGM metrics: Time in range (70-180 mg/dL), time below range, glucose management indicator (GMI) can serve as surrogate for HbA1c 1, 4
• Self-monitoring blood glucose: Many patients with type 1 diabetes require testing 6-10+ times daily, though individual needs vary 1

Additional Laboratory Tests Based on Clinical Context

Beyond the core HbA1c and uACR monitoring:

• Lipid profile: Assess cardiovascular risk, particularly important given increased cardiovascular disease risk in type 1 diabetes 2
• Blood ketones: For diagnosis of diabetic ketoacidosis and monitoring during treatment; recommended for individuals prone to ketosis with unexplained hyperglycemia or symptoms 2
• Thyroid function tests: Consider periodic screening given increased prevalence of autoimmune thyroid disease in type 1 diabetes
• Celiac disease screening: Consider in those with gastrointestinal symptoms or growth issues

Point-of-Care Testing Restrictions

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 point-of-care testing can provide opportunity for more timely treatment changes 1, it should not be used for diagnosis without proper certification 1.