Fructosamine

Also written as: Glycated Serum Protein, GSP

Sugar-coated blood proteins, reflecting average glucose over the past few weeks.

What it measures

The amount of blood proteins, mostly albumin, that have glucose attached to them. Because these proteins turn over quickly, the result reflects average glucose over the previous few weeks, a much shorter window than hemoglobin A1c.

Why a doctor orders it

Ordered when a shorter term average of glucose is wanted, for example soon after a change in routine. Also used when hemoglobin A1c may be unreliable, such as with anemia, altered red blood cell lifespan, or pregnancy.

What is generally associated with a higher result

Broadly associated with higher average blood glucose over the preceding few weeks.

What is generally associated with a lower result

Broadly associated with lower average glucose, but also with low blood protein levels, since the test depends on albumin. States that speed up protein turnover, including thyroid, kidney, and liver conditions, are linked with lower values independent of glucose.

Everyday things that move this number

Not every shift in a value reflects disease. These are ordinary factors known to affect this particular measurement:

Blood protein and albumin levels, which the test depends on
High dose vitamin C supplements
Pregnancy
Thyroid status
It reflects weeks of glucose, so a single unusual day barely moves it

Questions to take to your appointment

Was this chosen instead of A1c for a reason that applies to me?
Should albumin be measured alongside it to check the result is trustworthy?
How far apart should measurements be, given the short window it reflects?

Build a printable questionnaire with your own results →

Where to read more

MedlinePlus, from the US National Library of Medicine, publishes patient-facing pages on individual lab tests and is a reliable next stop: medlineplus.gov/lab-tests .

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