What are the recommended initial investigations for a patient presenti

Guideline-aligned answer with reasoning, red flags and references. Clinically reviewed by Dr Kola Tytler MBBS CertHE MBA MRCGP.

For a patient presenting with hyperglycaemia in primary care, the recommended initial investigations include:

Confirming hyperglycaemia diagnosis: Measure blood glucose levels, preferably plasma glucose, as patient-held glucose meters are calibrated to plasma glucose equivalents ,.
Assess diabetes subtype: In adults, make an initial clinical diagnosis of type 1 diabetes considering features such as ketosis, rapid weight loss, age under 50 years, BMI below 25 kg/m2, and personal or family history of autoimmune disease, but do not rely on age or BMI alone .
Diabetes-specific autoantibodies: Measure diabetes-specific autoantibodies in adults with suspected type 1 diabetes at initial diagnosis to support classification, ideally quantitative tests for at least two different autoantibodies .
Serum C-peptide: Do not routinely measure serum C-peptide at initial diagnosis; consider it only if autoantibody results are negative and diabetes classification remains uncertain .
HbA1c measurement: Measure HbA1c to assess average blood glucose control over the preceding 2–3 months and to support diagnosis and management planning ,.
Urine albumin:creatinine ratio (ACR) and serum creatinine: Assess kidney function and detect proteinuria as part of baseline evaluation, especially in type 1 diabetes, to identify risk of diabetic kidney disease ,.

What are the recommended initial investigations for a patient presenting with hyperglycaemia in primary care?