Type 2 diabetes in adults
Investigations
1st investigations to order
fasting plasma glucose
Test
Order after a minimum 8-hour fast. Bear in mind that a repeat confirmatory test is required for diagnosis in most cases, unless severe symptoms are present.
Result
≥7.0 mmol/L (≥126 mg/dL)
HbA1c
Test
Reflects degree of hyperglycaemia over the preceding 3 months.
Bear in mind that a repeat confirmatory test is required for diagnosis in most cases, unless severe symptoms are present.
HbA1c is also used to monitor glycaemic control.
Result
≥48 mmol/mol (≥6.5%)
2-hour post-load glucose after 75 g oral glucose
Test
Plasma glucose is measured 2 hours after 75 g oral glucose load.
Bear in mind that a repeat confirmatory test is required for diagnosis in most cases, unless severe symptoms are present.
Result
≥11.1 mmol/L (≥200 mg/dL)
random plasma glucose
Test
Non-fasting test. Bear in mind that a repeat confirmatory test is required for diagnosis in most cases, unless the patient has severe symptoms.
Used for rapid assessment of glucose status if symptoms such as polyuria, polydipsia, or weight loss are present.
Result
≥11.1 mmol/L (≥200 mg/dL)
Investigations to consider
fasting lipid profile
Test
Dyslipidaemia is common in type 2 diabetes.
Result
may show high LDL, low HDL, and/or high triglycerides
urine ketones
Test
Check urine ketones at diagnosis if the patient is symptomatic of hyperglycaemia (polyuria, polydipsia, weakness) and volume depletion (dry mucous membranes, poor skin turgor, tachycardia, hypotension, and, in severe cases, shock). Continue to monitor throughout the course of disease.
If increased ketone levels are left untreated, they can lead to progressive dehydration and diabetic ketoacidosis (DKA). DKA is a severe, life-threatening complication of diabetes. More commonly seen in people with type 1 diabetes, DKA may also occur in people with type 2 diabetes, particularly in the presence of an underlying infection (or other stressors) or following cardiovascular events, malignancy, antipsychotic medication, and concomitant treatment with sodium-glucose co-transporter-2 (SGLT2) inhibitors.[71][72][73][74]
See our topic 'Diabetic ketoacidosis'.
Result
positive in instances of ketoacidosis
albumin to creatinine ratio (ACR)
serum creatinine and estimated GFR
Test
GFR is calculated according to the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) or Modification of Diet in Renal Disease (MDRD) formulas. The CKD-EPI formula is now recommended by the Kidney Disease Outcomes Quality Initiative (KDOQI) because it removes bias at higher GFR levels, allowing for reporting across a full range. [ Glomerular Filtration Rate Estimate by CKD-EPI Equation Opens in new window ]
Result
may show renal insufficiency
ECG
Test
Baseline assessment. A normal ECG does not rule out coronary artery disease. Patients with an abnormal resting ECG may require further cardiac investigation.[34]
Result
may indicate prior ischaemia
ankle-brachial pressure index (ABPI)
Test
A non-invasive tool to detect peripheral arterial disease (PAD), which has a high prevalence in people with diabetes. The National Institute for Health and Care Excellence in the UK recommends that ABPI should be performed in people with suspected PAD.[85]
Due to the potential for calcification of the arteries from atherosclerotic peripheral vascular disease (which falsely elevates the ankle-brachial index), toe pressure testing is often done as an adjunct to ABPI testing. A normal ABPI value is 1.0; a normal toe pressure value is 0.7. Do not exclude a diagnosis of PAD in people with diabetes based on a normal or raised ABPI.[85]
Result
≤0.9 is abnormal
random C-peptide
Test
Routine serum C-peptide measurement should not be used to confirm type 1 diagnosis; however, if a negative diabetes-specific autoantibody result is obtained, or if diabetes classification remains uncertain at a subsequent visit, serum C-peptide measurement could be considered.[75]
If C-peptide testing is indicated, bear in mind that it has better discriminative value the longer the test is done after initial presentation.[75]
In clinical practice, serum C-peptide testing can be paired with blood glucose.[75]
Result
normal or high
autoantibody testing
Test
If the patient has received an initial diagnosis of type 2 diabetes, but has persistently/significantly raised HbA1c despite oral medication or persistent osmotic symptoms/weight loss, consider testing for autoantibodies, as the patient may have type 1 diabetes and may have been wrongly diagnosed with type 2 diabetes.
Diabetes-specific autoantibodies are routinely measured in adults with an initial diagnosis of type 1 diabetes, taking into account that the false negative rate of diabetes-specific autoantibody tests is lowest at the time of diagnosis and that the false negative rate can be reduced by carrying out quantitative tests for 2 different diabetes-specific autoantibodies (with at least 1 being positive).
Autoantibodies to glutamic acid decarboxylase 65 (GAD), islet cell antibodies (ICA), insulin antibodies, antibodies to tyrosine phosphatase-related islet antigen-2 (IA-2 and IA-2beta), and zinc-transporter-8 antibodies (ZnT8) can help to identify individuals with immune-mediated diabetes, although these antibodies fade with time after onset of illness.[34][76][77][78]
Result
negative
liver function tests
Test
May identify people with non-alcoholic fatty liver disease (NAFLD). The prevalence of NAFLD in people with type 2 diabetes is thought to be 40% to 70%.[86]
Result
may be elevated
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