system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does the A1C test measure your blood glucose levels over the last 3 months instead of what it is at the time blood was drawn?
gpt
Red blood cells in your body live for about three months. That's where the three month span of the test comes from. As you live, glucose binds to this red blood cells, the more glucose in your blood the more red blood cells it binds to. They test the percentage of red blood cells that have glucose bound to them, and this reflects a three month average of blood glucose.