Initial Blood Work for Type 2 Diabetes with Neuropathy
The most critical initial blood work for diabetic neuropathy is HbA1c to assess glycemic control, as diabetic neuropathy is a diagnosis of exclusion requiring evaluation for other treatable causes of neuropathy. 1
Essential Laboratory Testing
Primary Glycemic Assessment
- HbA1c measurement is the cornerstone test, as hyperglycemia is the most important etiology for neuropathy progression in type 2 diabetes 2, 3
- HbA1c levels above 8.5% correlate with significant electrophysiologic deterioration 3
- Duration of diabetes and HbA1c levels are the two factors most significantly associated with neuropathy diagnosis 2
Screening for Alternative Causes
Since diabetic neuropathy is a diagnosis of exclusion, you must rule out other treatable neuropathies that can coexist in diabetic patients 1:
- Vitamin B12 levels: Deficiency should be considered as an alternative cause of neuropathy, particularly in patients on metformin 4
- Thyroid function tests (TSH): Hypothyroidism can cause neuropathy 4
- Renal function (creatinine, eGFR): Uremic neuropathy from diabetic kidney disease must be excluded 4
- Urine albumin-to-creatinine ratio: Albuminuria is a potent predictor of diabetic peripheral neuropathy with an odds ratio of 1.85 5
Additional Metabolic Parameters
- Lipid panel: Dyslipidemia control may slow neuropathy progression in type 2 diabetes 1
- Liver function tests (AST, ALT): To evaluate for nonalcoholic fatty liver disease, which should be assessed at diagnosis 1
Important Clinical Caveats
The B12 Controversy
- B12 supplementation is only indicated when deficiency is confirmed 4
- There is no evidence that B12 supplementation in patients with normal levels improves neuropathic symptoms 4
- Do not supplement B12 indiscriminately without documented deficiency 4
Timing Considerations
- Blood work should be obtained at the time of neuropathy diagnosis 1
- Annual monitoring of HbA1c and renal function is required thereafter 1
- Urine albumin-to-creatinine ratio should be checked annually, as it predicts neuropathy risk 5
What NOT to Order Routinely
- Electrophysiological testing is rarely needed except when clinical features are atypical or diagnosis is unclear 1
- Extensive autoimmune panels are not indicated unless clinical presentation suggests non-diabetic etiology 1
Risk Stratification Based on Results
The presence of the following laboratory findings increases neuropathy risk and indicates need for aggressive intervention: