What Is a Fasting Insulin Blood Test?

Fasting insulin measures how much insulin your pancreas produces to maintain normal blood sugar.

Normal Range

• Below 12 µIU/mL (some use below 10)
• Elevated = insulin resistance

HOMA-IR

• HOMA-IR = (fasting glucose × fasting insulin) ÷ 405
• Below 1.0 = optimal insulin sensitivity
• Above 2.5 = significant insulin resistance

Why Test Insulin?

• Detects insulin resistance BEFORE glucose rises
• Early marker of metabolic syndrome
• Guides lifestyle interventions

When to Test

• Family history of diabetes
• Obesity or PCOS
• Acanthosis nigricans (dark skin patches)