What tests and evaluations should be ordered for a comprehensive diabetes workup?

Diabetes Workup: Essential Laboratory and Diagnostic Testing

Initial Diagnostic Testing

For a comprehensive diabetes workup, order HbA1c, fasting plasma glucose (FPG), fasting lipid panel, serum creatinine with eGFR, and urine albumin-to-creatinine ratio (ACR) as your core laboratory tests. 1, 2, 3

Core Metabolic Panel

• HbA1c is essential for both diagnosis (≥6.5% confirms diabetes) and baseline glycemic control assessment 3
• Fasting plasma glucose (requires 8-12 hour fast) provides diagnostic confirmation when ≥126 mg/dL 4, 3
• Random plasma glucose ≥200 mg/dL with hyperglycemia symptoms can diagnose diabetes without fasting 3
• Confirm abnormal results with repeat testing on a subsequent day unless random glucose ≥200 mg/dL with classic symptoms 3

Cardiovascular Risk Assessment

• Fasting lipid panel (requires 8-12 hour fast) including total cholesterol, LDL-C, HDL-C, and triglycerides to assess cardiovascular risk 5, 4
• Target LDL-C <100 mg/dL, HDL-C >35 mg/dL, and triglycerides <200 mg/dL 6
• Blood pressure measurement at every visit, with target <135/85 mm Hg (or <130/80 mm Hg per current guidelines) 5, 6

Renal Function Screening

• Serum creatinine with calculated eGFR to assess kidney function and guide medication choices 5, 2
• Urine albumin-to-creatinine ratio (ACR) from random spot urine sample to screen for diabetic nephropathy 5, 2
• Annual screening for microalbuminuria is recommended once diabetes is established 5

Additional Laboratory Tests Based on Diabetes Type

Type 1 Diabetes Considerations

• Thyroid function tests (TSH, free T4) due to increased autoimmune thyroid disease risk 2
• Suspend biotin supplements 72 hours before thyroid testing to avoid assay interference 4
• Consider autoantibody testing (GAD, IA-2, ZnT8) if diabetes type is unclear 1, 7

Comprehensive Metabolic Assessment

• Basal insulin level (fasting) may help differentiate diabetes types in unclear cases 4, 7
• Liver function tests as part of comprehensive metabolic panel, especially before initiating certain medications 2, 4
• Complete blood count to establish baseline and screen for anemia 2

Physical Examination Components

Comprehensive Foot Examination

• Visual inspection of skin integrity, deformities, calluses, and ulcers 5, 2
• 10-g monofilament testing plus at least one additional test (pinprick, vibration with 128-Hz tuning fork, temperature sensation, or ankle reflexes) to assess for loss of protective sensation 5
• Pedal pulse assessment (dorsalis pedis and posterior tibial) to evaluate peripheral arterial disease 5, 2
• Perform comprehensive foot exam at least annually, with inspection at every visit 5

Cardiovascular and Vascular Assessment

• Ankle-brachial index (ABI) testing for patients with symptoms of claudication, decreased walking speed, leg fatigue, or absent/decreased pedal pulses 5
• Urgent vascular imaging indicated if ABI <0.5, toe pressure <30 mmHg, or TcPO2 <25 mmHg 5
• Orthostatic blood pressure measurements when autonomic neuropathy suspected (dizziness upon standing) 1, 2

Ophthalmologic Evaluation

• Dilated comprehensive eye examination by ophthalmologist or optometrist shortly after type 2 diabetes diagnosis 5
• For type 1 diabetes, initial exam within 5 years of diagnosis 5
• Annual follow-up exams recommended, though may extend to every 2-3 years after normal exams 5

Neurological Assessment

• Screen for distal symmetric polyneuropathy at diagnosis of type 2 diabetes and 5 years after type 1 diabetes diagnosis, then annually 5
• Assess for autonomic neuropathy symptoms including gastroparesis (early satiety, nausea, bloating), sexual dysfunction, and orthostatic hypotension 1, 2
• Electrophysiological testing rarely needed except when clinical features are atypical 5

Critical Pre-Test Instructions

Fasting Requirements

• 8-12 hour fast required for FPG, lipid panel, and basal insulin testing 4
• Only water permitted during fast—no coffee, tea, or juices 4
• Regular medications can be taken with small sips of water unless otherwise directed 4

Medication and Supplement Considerations

• Suspend biotin 72 hours before testing as it interferes with thyroid and other immunoassays 4
• If patient takes levothyroxine, administer after blood draw that day 4
• Avoid alcohol 48 hours before testing as it affects liver function and glucose 4
• Avoid intense exercise 24 hours before blood draw 4

Common Pitfalls to Avoid

• Do not skip foot examination—this is the most commonly neglected component that leads to preventable complications 2
• Do not forget to assess vaccination status (influenza, pneumococcal) as part of comprehensive care 1, 2
• Do not neglect psychosocial screening—depression and diabetes distress significantly impact outcomes and should be assessed with direct questions like "How are you coping emotionally with diabetes?" 1, 2
• Do not order cortisol testing after 9:00 AM if included in workup, as reference values are morning-specific 4
• Do not assume diabetes type—directly ask "What type of diabetes do you have?" and document age at diagnosis and presenting symptoms 1