What labs should be checked to monitor diabetic patients?

Laboratory Monitoring for Diabetic Patients

All diabetic patients require routine measurement of 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 monitoring. 1, 2

Core Laboratory Tests

Hemoglobin A1c (HbA1c)

• Measure HbA1c every 3 months in patients not meeting glycemic targets or with recent treatment changes 1, 2, 3
• Measure at least every 6 months once acceptable, individualized targets are achieved 1, 2, 3
• Target HbA1c <7% (<53 mmol/mol) for most non-pregnant adults with diabetes 1
• Only use NGSP-certified methods performed in accredited laboratories 1, 2, 3
• HbA1c reflects average glucose control over the preceding 60-90 days 3

Important caveat: HbA1c may be unreliable in conditions affecting red blood cell turnover including sickle cell disease, pregnancy, hemodialysis, recent blood loss or transfusion, and erythropoietin therapy—in these cases, use only plasma glucose criteria 4, 3

Fasting Plasma Glucose (FPG)

• Measure FPG periodically to monitor glycemic control and therapeutic response 5, 6
• Collect samples after at least 8 hours of fasting 2, 3
• Use tubes containing granulated citrate buffer or place samples immediately in ice-water slurry and centrifuge within 15-30 minutes to minimize glycolysis 2, 3

Urine Albumin-to-Creatinine Ratio (uACR)

• Measure annually in all adults with diabetes using morning spot urine samples 2, 3
• First morning void samples are preferred to minimize variability 2
• Increase 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 2, 3
• For type 1 diabetes, begin annual testing in pubertal or post-pubertal individuals 5 years after diagnosis 4

Additional Monitoring Based on Clinical Context

Liver Function Tests

• Measure liver enzymes prior to initiating therapy with certain medications like pioglitazone 5
• Monitor periodically thereafter per clinical judgment 5
• If ALT levels exceed 2.5 times the upper limit of normal, evaluate more frequently 5
• Discontinue therapy if ALT remains >3 times the upper limit of normal or if jaundice develops 5

Lipid Profile

• Measure lipid panel to assess cardiovascular risk, particularly in patients with hypertension, low HDL cholesterol, or high triglycerides 3
• Adult diabetic patients should have fasting lipid profile measured at least annually 7

Ketone Testing

• Blood ketone (β-hydroxybutyrate) measurement should be used for diagnosis of diabetic ketoacidosis and may be used for monitoring during treatment 1, 4, 3
• Individuals prone to ketosis (type 1 diabetes, history of DKA, or on SGLT2 inhibitors) should measure ketones when experiencing unexplained hyperglycemia or symptoms of ketosis 1, 3
• Blood ketone determinations using the nitroprusside reaction should not be used to monitor DKA treatment 1

C-Peptide

• Measure C-peptide to help distinguish type 1 from type 2 diabetes in ambiguous cases, such as individuals with type 2 phenotype who present in ketoacidosis 2, 4, 3
• For insulin pump therapy coverage, measure fasting C-peptide when simultaneous fasting plasma glucose is <220 mg/dL 2

Special Populations

Gestational Diabetes

• Test all pregnant women with risk factors for diabetes at the first prenatal visit using standard diagnostic criteria 1
• Evaluate all pregnant women not previously known to have diabetes for gestational diabetes at 24-28 weeks of gestation 1
• Women with gestational diabetes should be tested for prediabetes or diabetes 4-12 weeks postpartum 1
• Lifelong screening at least every 3 years is required for women with a history of gestational diabetes 1, 3

Prediabetes

• Patients with prediabetes should be tested yearly 3

Quality Assurance Considerations

• Point-of-care HbA1c testing for diabetes screening and diagnosis should be restricted to FDA-approved devices at CLIA-certified laboratories performing testing of moderate complexity or higher 1, 4, 3
• Glucose measurement should have analytical imprecision ≤2.4%, bias ≤2.1%, and total error ≤6.1% 2
• Urine albumin measurement should meet performance goals: between-day precision ≤6%, bias ≤7% to 13%, and total allowable error ≤24% to 30% 2

Common Pitfalls to Avoid

• Do not use urine glucose testing for routine care of diabetic patients 1
• HbA1c does not provide information about glycemic variability or hypoglycemia—use self-monitoring of blood glucose or continuous glucose monitoring for these assessments 4, 3
• Avoid timed urine collections for albumin in clinical practice; these should be reserved for research settings only 4
• Do not rely solely on HbA1c in patients with conditions affecting red blood cell turnover—use alternative glucose monitoring methods 4, 3