Question

Half life of insulin

• A. \(<1 \, \text{min} \)
• B. 5-6 mins
• C. 30-40 mins
• D. 1-2 hrs

Hint:

Insulin has a short half-life, typically 5-6 minutes, which is important for regulating its therapeutic effects.

Answer 1

The Correct Option is B

Insulin is cleared rapidly from the bloodstream, mainly through hepatic and renal degradation, giving it a short plasma half-life of approximately 5-6 minutes. This rapid turnover is why insulin needs to be secreted (or administered) continuously or in repeated doses to maintain its blood-glucose-lowering effect, unlike hormones with longer half-lives that persist in circulation for hours.

Therefore, the correct answer is 5-6 mins.

Answer 2

Another way to approach this is by considering the physiological consequence of each half-life option, since insulin needs frequent secretion to maintain blood glucose control.

1. \(<1\,\text{min}\): If insulin's half-life were this short, it would barely have time to reach and act on peripheral tissues before being eliminated, which does not match its known biological effectiveness.
2. 5-6 mins: This half-life is long enough for insulin to circulate and bind its receptors, yet short enough to explain why insulin secretion must be tightly and continuously regulated to control blood glucose — matching its physiological behavior.
3. 30-40 mins: A half-life this long would mean insulin lingers in circulation much longer than observed, which would make blood glucose regulation far less responsive than it actually is.
4. 1-2 hrs: This is inconsistent with how quickly insulin levels are known to fall after a glucose-stimulated secretion peak.

The physiological need for tight, minute-to-minute glucose control is best explained by a half-life of 5-6 minutes.

Therefore, the correct answer is 5-6 mins.