Gluconeogenesis from amino acids begins within how many hours after the last meal?

• A. Within 1-2 hours
• B. Within 8-12 hours
• C. Within 4-6 hours after the last meal
• D. After 24 hours

Answer: (C)

As soon as the post-meal period ends, the body begins shifting from absorbing nutrients to maintaining blood glucose through fasting metabolism. The liver starts tapping into glucogenic substrates from the breakdown of body proteins, and within about four to six hours after the last meal, enough glucogenic amino acids become available to start contributing to gluconeogenesis. Alanine, a key amino acid released from muscle, is converted to pyruvate and then to glucose, with other glucogenic amino acids joining in to support hepatic glucose production.

This timing fits the transition from the immediate postprandial state, where glycogen is still helping uphold blood glucose, to the early fasting state where amino acids begin to supplement glucose output. It’s too early to rely predominantly on amino acids for gluconeogenesis within 1-2 hours when the body is still in the fed state, and the onset described here occurs before 8–12 hours, with longer fasting sustaining ongoing gluconeogenesis beyond 24 hours.