When are blood insulin laboratory measurements useful?

From the Guidelines

Blood insulin lab measurements are most useful when diagnosing or monitoring conditions related to insulin dysregulation, such as diabetes, hypoglycemia, or insulinomas, and should be prioritized in these cases to improve morbidity, mortality, and quality of life outcomes.

Key Considerations

• Insulin testing is helpful in distinguishing between type 1 and type 2 diabetes, as type 1 patients typically have low insulin levels while type 2 patients often have normal or elevated levels despite high blood glucose 1.
• Fasting insulin levels are commonly ordered alongside glucose tests to calculate insulin resistance using indices like HOMA-IR, providing valuable information for diagnosis and treatment planning 1.
• For suspected reactive hypoglycemia, insulin measurements during a glucose tolerance test can reveal inappropriate insulin secretion, guiding further management and treatment decisions 1.
• In cases of suspected insulinoma (insulin-producing tumor), a 72-hour fasting test with simultaneous insulin and glucose measurements is the gold standard diagnostic approach, allowing for accurate diagnosis and treatment planning 1.

Clinical Applications

• Blood insulin lab measurements can help evaluate the impact of nutrition, physical activity, and medication management on glucose levels, informing treatment adjustments and improving patient outcomes 1.
• Glucose monitoring may also be useful in assessing hypoglycemia, glucose levels during intercurrent illness, or discrepancies between measured A1C and glucose levels, ensuring timely and effective interventions 1.
• The timing of insulin testing is critical, with fasting samples providing baseline information and post-prandial or post-glucose challenge samples helping to evaluate insulin response to carbohydrate intake, guiding personalized treatment plans 1.

Evidence-Based Recommendations

• The most recent and highest quality study 1 supports the use of blood insulin lab measurements in diagnosing and monitoring conditions related to insulin dysregulation, emphasizing the importance of accurate and timely diagnosis and treatment to improve patient outcomes.
• The American Diabetes Association recommends the use of blood insulin lab measurements in specific clinical scenarios, such as diagnosing diabetes, monitoring insulin therapy, and evaluating hypoglycemia, highlighting the importance of evidence-based practice in diabetes management 1.

From the FDA Drug Label

Patients and caregivers must be educated to recognize and manage hypoglycemia. Self-monitoring of blood glucose plays an essential role in the prevention and management of hypoglycemia; increased frequency of blood glucose monitoring is recommended In patients at higher risk for hypoglycemia and patients who have reduced symptomatic awareness of hypoglycemia, increased frequency of blood glucose monitoring is recommended.

Blood insulin lab measurements are useful in the following situations:

• Hypoglycemia management: to confirm hypoglycemia and monitor the patient's response to treatment
• Changes in insulin regimen: to closely monitor blood glucose levels when changes are made to the insulin regimen, such as a change in insulin strength, manufacturer, type, injection site, or method of administration 2
• High-risk patients: in patients at higher risk for hypoglycemia, such as those with renal or hepatic impairment, or those taking medications that increase the risk of hypoglycemia 3
• Reduced symptomatic awareness: in patients who have reduced symptomatic awareness of hypoglycemia, such as those with longstanding diabetes or diabetic nerve disease.

From the Research

Blood Insulin Lab Measurements

Blood insulin lab measurements are useful in various clinical scenarios, including:

• Diagnosis and management of diabetes mellitus, as stated in 4
• Monitoring of insulin therapy, where reliable quantification of insulin is crucial for clinical purposes such as diagnosis and treatment of diabetes, as mentioned in 5
• Differentiation between type 1 and type 2 diabetes, as well as monitoring the effectiveness of insulin analogues, as discussed in 6 and 7

Clinical Applications

Some specific clinical applications of blood insulin lab measurements include:

• Evaluating the pharmacokinetics and pharmacodynamics of insulin analogues, such as insulin degludec and insulin aspart, as described in 6
• Comparing the duration of action of different insulin formulations, such as insulin lispro protamine suspension, insulin glargine, and insulin detemir, as reported in 8
• Assessing the glucose-lowering activity of insulin and its analogues, as measured by glucose clamps, as mentioned in 8

Analytical Methods

Various analytical methods are available for measuring insulin levels, including:

• Immunoassays, such as enzyme-linked immunosorbent assay (ELISA), chemiluminescence immunoassay (CLIA), and radioimmunoassay (RIA), as summarized in 5
• Chromatographic assays, such as high performance liquid chromatography coupled with ultraviolet detection (HPLC-UV) and liquid chromatography with tandem mass spectrometry (LC-MS/MS), as discussed in 5