fructosamine

It's not a direct glucose concentration in the same way that a fasted glucose measurement is, but it is related to glucose exposure over time.

However, whenever HbA1c is discussed, it is also worth mentioning the fructosamine assay.

Fructosamine reflects a shorter window, roughly the previous two to three weeks, because it measures the glycated serum proteins rather than glycated hemoglobin.

Now, this can make it particularly useful when someone has recently changed their diet or lifestyle and wants a more responsive marker.

If someone has gone low carb or ketogenic or carnivore, waiting three months for an HbA1c to fully reflect the change may feel like watching paint dry in a damp shed, whereas fructosamine can give a, a shorter term view, and it's more reliable, by the way.