What laboratory tests should be monitored for patients with diabetes?

Laboratory Monitoring for Patients with Diabetes

Hemoglobin A1c should be measured every 3 months until glycemic targets are achieved, then at least every 6 months, with additional monitoring of fasting plasma glucose and annual urine albumin-to-creatinine ratio to screen for diabetic kidney disease. 1

Core Laboratory Tests

Hemoglobin A1c (HbA1c)

• Measure routinely every 3 months until acceptable, individualized targets are reached, then no less than every 6 months in most individuals with diabetes 1
• Perform at least twice yearly in patients meeting treatment goals with stable glycemic control 1
• Perform quarterly in patients whose therapy has changed or who are not meeting glycemic goals 1
• Only use NGSP-certified methods performed in accredited laboratories 1
• Target HbA1c <7% (<53 mmol/mol) for many nonpregnant adults with diabetes 1

Important caveat: HbA1c may not be reliable in conditions affecting red blood cell turnover, including sickle cell disease, pregnancy, hemodialysis, recent blood loss or transfusion, erythropoietin therapy, hemolytic anemia, glucose-6-phosphate dehydrogenase deficiency, and end-stage kidney disease 1. In these situations, use only plasma glucose criteria for diagnosis and monitoring 2.

Fasting Plasma Glucose (FPG)

• Measure after at least 8 hours of fasting 1
• Collect samples in tubes containing citrate buffer or place immediately in ice-water slurry and centrifuge within 15-30 minutes to minimize glycolysis 2, 3
• Use for diagnosis when HbA1c is unreliable due to conditions affecting red blood cell turnover 2

Urine Albumin-to-Creatinine Ratio (uACR)

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

Blood Glucose Monitoring

Self-Monitoring of Blood Glucose (SMBG)

• Patients using multiple daily insulin injections should perform SMBG at least 4 times per day 1
• All insulin-treated patients should perform SMBG at a frequency appropriate for their insulin regimen 1
• Patients treated with sulfonylureas should monitor to detect and prevent asymptomatic hypoglycemia 1
• For patients on less frequent insulin injections or noninsulin therapies, SMBG frequency should be sufficient to facilitate reaching glucose goals 1

Continuous Glucose Monitoring (CGM)

• Real-time CGM should be used in conjunction with insulin in teens and adults with type 1 diabetes who are not meeting glycemic targets or have hypoglycemia unawareness 1
• Consider intermittently scanned CGM (flash CGM) in adults with type 1 diabetes not meeting targets or experiencing hypoglycemia 1
• CGM is not currently recommended for screening or diagnosis of prediabetes or diabetes 1

Ketone Testing

• Individuals prone to ketosis (type 1 diabetes, history of diabetic ketoacidosis, or treated with SGLT2 inhibitors) should measure ketones in urine or blood if they have unexplained hyperglycemia or symptoms of ketosis 1
• Use specific measurement of β-hydroxybutyrate in blood for diagnosis of diabetic ketoacidosis and may be used for monitoring during treatment 1, 4
• Blood ketone determinations using nitroprusside reaction should not be used to monitor treatment of diabetic ketoacidosis 1

Additional Laboratory Tests

Lipid Profile

• Measure to assess cardiovascular risk factors, particularly in patients with hypertension, low HDL cholesterol, or high triglycerides 2
• Adult diabetic patients should measure fasting lipid profile at least annually or every 2 years if low-risk lipid values 5

C-Peptide

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

Autoantibody Testing

• Use standardized islet autoantibody tests for classification of diabetes in adults when there is phenotypic overlap between type 1 and type 2 diabetes 4
• Key autoantibodies include islet cell autoantibodies, glutamic acid decarboxylase autoantibodies, insulin autoantibodies, tyrosine phosphatase autoantibodies, and zinc transporter 8 autoantibodies 4

Special Populations

Gestational Diabetes

• Women with gestational diabetes should perform fasting and postprandial blood glucose monitoring for optimal glucose control 1
• Test for prediabetes or diabetes 4-12 weeks postpartum using nonpregnant oral glucose tolerance test criteria 1
• Perform lifelong screening for diabetes at least every 3 years using standard nonpregnant criteria 1, 2

Prediabetes

• Patients with prediabetes should be tested yearly 2

Medication-Specific Monitoring

Pioglitazone

• Evaluate serum ALT (alanine aminotransferase) prior to initiation and periodically thereafter 6
• If ALT levels are 1-2.5 times upper limit of normal, proceed with caution and monitor more frequently 6
• If ALT exceeds 3 times upper limit of normal, repeat testing promptly and discontinue if levels remain elevated or if jaundice develops 6
• Do not initiate if ALT exceeds 2.5 times upper limit of normal 6

Metformin

• Monitor FPG and HbA1c periodically to assess glycemic control and therapeutic response 7

Common Pitfalls to Avoid

• 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, 2
• Urine glucose testing is not recommended for routine care of patients with diabetes 1
• Timed urine collections for albumin should be done only in research settings and should not guide clinical practice 4
• HbA1c does not provide a measure of glycemic variability or hypoglycemia, which are important factors in diabetes management 2, 4
• For patients with conditions interfering with HbA1c interpretation, use alternative approaches such as SMBG, CGM, or glycated serum protein assays 2