Investigations

1st investigations to order

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Confirm with a repeat HbA1c or another diagnostic test.[2] HbA1c is also used to monitor glycemic control, usually every 3 months.

Result

6.5% or greater

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Order after a minimum 8-hour fast. Confirm an elevated result with an HbA1c (which can be done on the same sample), a second fasting plasma glucose, or another diabetes diagnostic test.[2]

Result

>125 mg/dL

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Result
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Nonfasting test. Convenient, but less accurate than either fasting plasma glucose, HbA1c, or 75 g oral glucose tolerance test.[2] Used for rapid assessment of glucose status if symptoms such as polyuria, polydipsia, or weight loss are present.

Result

≥200 mg/dL

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Result
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More costly and inconvenient than fasting plasma glucose or HbA1c. Diabetes should be confirmed on a separate occasion with another diagnostic test.[2]

Result

≥200 mg/dL

Investigations to consider

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Result
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Dyslipidemia is common in type 2 diabetes.

Result

may show high LDL, low HDL, and/or high triglycerides

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Result
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Urine ketones should be checked if patients are symptomatic of hyperglycemia (polyuria, polydipsia, weakness) and volume depletion (dry mucous membranes, poor skin turgor, tachycardia, hypotension, and, in severe cases, shock) at diagnosis or throughout course of disease. Ketoacidosis is a common presentation of type 1 diabetes, but can also occur in type 2 diabetes.[39][40][41]

Result

positive in instances of ketoacidosis

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Result
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Not done routinely for diagnosis of diabetes, but may be useful in differentiating type 1 and type 2 diabetes.[42] Absolute insulin deficiency is a key feature of type 1 diabetes, which results in low (<0.2 nanomol/L) or undetectable levels of plasma C-peptide.[2][42] C-peptide results must be interpreted in clinical context of disease duration, comorbidities, and family history.[43]

Result

>1 nanomol/L

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Result
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Indicates nephropathy and suggests possible other microvascular damage. Monitored yearly.

May be assessed with albumin-to-creatinine ratio in a random urine sample.[2]

Result

may be increased

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Result
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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 ]

Result

may show renal insufficiency

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Result
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Baseline assessment. A normal ECG does not rule out coronary artery disease. Patients with an abnormal resting ECG may require further cardiac investigation.[2]

Result

may indicate prior ischemia

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Result
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A noninvasive tool to detect peripheral arterial disease (PAD), which has a high prevalence in patients with diabetes. The American Diabetes Association recommends that ABI should be performed in patients with symptoms of PAD.[2] Can be used to screen for PAD.

Result

≤0.9 is abnormal

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Result
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Patients should be referred to an ophthalmologist at the time of diagnosis of type 2 diabetes.[2]

Result

may show retinopathy

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