HbA1c measurements can be artificially low in individuals with high red blood cell turnover and artificially high in individuals with long-lived red blood cells or a microcytic pattern.

“this is potentially misleading because if a red blood cell has a very short life for example i see this in a couple of my patients including a patient who's recovering from prostate cancer who still has some gi bleeding issues patients with gastritis etc women with a heavy menstrual period so people who are losing significant amounts of blood have a higher turnover red blood cells they're going to have an artificially low hemoglobin a1c conversely people who have red blood cells that stick around a very long time people with a microcytic pattern meaning they have very small red blood cells that are less likely to get chewed up in the splenic system which is where we ultimately um kind of break down red blood cells they're going to have an artificially elevated hemoglobin a1c because their red blood cells are living longer on average than um the than the typical person which is about 90 days”