Fructosamine
A measure of average blood sugar over the previous two to three weeks — a shorter window than HbA1c's three months. It is used mainly as an alternative when HbA1c is unreliable, or to see the effect of a diabetes treatment change sooner.
What it measures
Fructosamine reflects how much glucose has attached to proteins in the blood (mainly albumin) over the lifespan of those proteins, giving an average blood-sugar level for the past two to three weeks. This is its defining feature and the source of its two uses. First, it provides a shorter-term picture than HbA1c (which reflects about three months), so it can show the effect of a change in diabetes treatment, or the impact of pregnancy, more quickly. Second, and most importantly, it is used when HbA1c is unreliable — HbA1c depends on red blood cells and their haemoglobin, so it can be misleading in people with certain haemoglobin disorders, recent blood loss or transfusion, or conditions that change red-cell lifespan; fructosamine, which does not depend on red cells, sidesteps this. However, it is affected by anything that changes protein levels (such as low albumin in kidney or liver disease), and it is a less standardised, less widely used test than HbA1c.
What a high value can mean
- Higher average blood sugar over the past 2–3 weeks — poorer diabetes control, or newly high glucose.
- Useful where HbA1c is unreliable — haemoglobin disorders, recent blood loss/transfusion, altered red-cell lifespan.
- A rise after a treatment change — shows worsening control sooner than HbA1c would.
What a low value can mean
- Lower average blood sugar — good control, or a fall after treatment.
- Falsely low from low albumin — kidney disease (nephrotic syndrome), liver disease, or protein loss can lower fructosamine independently of glucose.
When to discuss with a doctor
Fructosamine is a second-line glucose test, not a routine one. It is worth using when HbA1c cannot be trusted — for example with a haemoglobin variant, after recent bleeding or a transfusion, or when red-cell turnover is abnormal — because it gives an average glucose without relying on red cells. It is also useful to judge the effect of a diabetes treatment change over a few weeks rather than waiting three months for HbA1c. Its result must be interpreted with albumin, since a low albumin can falsely lower it. Mediora.AI shows fructosamine alongside HbA1c and glucose so the glucose picture is read with the right test; the diabetes management decision belongs with your doctor.