Fructosamine

Ranges differ between methods; the figure is lower when blood protein (albumin) is low, for example in kidney disease with protein loss, liver disease or poor nutrition.

Fructosamine is the name for blood proteins, mainly albumin, that have glucose attached to them. Because these proteins are replaced every two to three weeks, the figure reflects the average blood sugar over that time, a shorter window than HbA1c, which covers about three months.

Doctors request it as an alternative to HbA1c when HbA1c cannot be trusted, for example in some anaemias, with haemoglobin variants or in pregnancy, or when a quick check of how sugar control has changed over the last few weeks is wanted.

• Diabetes and pre-diabetes, over the preceding two to three weeks
• Steroid medicines
• An underactive thyroid
• A high blood protein level

• Better sugar control over the preceding weeks
• A low albumin, as in kidney disease with protein loss, liver disease or poor nutrition
• An overactive thyroid
• High vitamin C intake, in some methods

• A low albumin lowers it without any change in blood sugar
• Methods differ between laboratories
• A large vitamin C supplement on the day of the test can interfere

No fasting needed. It reflects the previous two to three weeks and is usually read alongside albumin. The trend over repeated tests is more useful than one value.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.