What this test measures
1,5-Anhydroglucitol (1,5-AG) is a naturally-occurring sugar found in serum at fairly stable levels in non-diabetics. It is filtered by the kidneys and reabsorbed almost completely — except when blood glucose rises above the renal threshold (~180 mg/dL), at which point glucose competitively inhibits 1,5-AG reabsorption and 1,5-AG is excreted. The result: 1,5-AG drops when there have been recent hyperglycaemic spikes.
It reflects glycaemic excursions and post-prandial peaks over the previous 1–2 weeks — a shorter window than HbA1c (~3 months) and a different concept from fasting plasma glucose. It is not a replacement for HbA1c but a complement, especially when post-prandial control is the issue.
Why it matters
In India, where post-prandial hyperglycaemia (often driven by carbohydrate-rich meals) is a particular challenge in type 2 diabetes management, 1,5-AG can help reveal swings that HbA1c smooths out. It is also useful in pregnancy / gestational diabetes follow-up, when HbA1c can be misleading due to altered red cell turnover, and in patients with haemoglobinopathies where HbA1c is unreliable.
However, 1,5-AG is not yet a routine test in India — it is offered in some specialised endocrine centres and reference labs. The American Diabetes Association notes it as a possible complementary marker but does not recommend it as a substitute for HbA1c.
How to prepare
No fasting required. Continue medications and usual diet. Mention any recent kidney disease (the test is unreliable in CKD with reduced renal threshold), pregnancy, dialysis, or glucosuria-producing drugs (SGLT2 inhibitors — which cause glucosuria and lower 1,5-AG independent of blood glucose).
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| 1,5-Anhydroglucitol (µg/mL)[1][2] | > 10 (typical lab range; >14 considered normal) | Low 1,5-AG (<10) — recent post-prandial hyperglycaemia with glucose excursions above the renal threshold. Particularly informative when HbA1c looks acceptable but post-prandial glucose is poorly controlled. Also lowered by SGLT2 inhibitors (drug-induced glucosuria), CKD with low renal threshold, dialysis. | High 1,5-AG — non-specific; usually represents good glycaemic control over the past 1–2 weeks (no glucose excursions above renal threshold). Can be artefactually high after acarbose use or specific dietary changes. |
Glycaemic markers — what each tells you
| Marker | Window | Strength | Limitations |
|---|---|---|---|
| Fasting Plasma Glucose | Instantaneous (this moment) | Standard diagnostic | Misses post-prandial peaks |
| HbA1c | ~ 3 months | Standard long-term control marker | Affected by haemoglobinopathies, anaemia, pregnancy |
| Fructosamine | ~ 2 – 3 weeks | Useful when HbA1c unreliable | Affected by albumin, protein turnover |
| 1,5-AG | ~ 1 – 2 weeks; specifically post-prandial spikes | Reveals hidden glycaemic excursions | Affected by CKD, SGLT2 inhibitors, dialysis |
| CGM (continuous glucose monitoring) | Continuous | Most detailed; time-in-range | Cost, availability |
Frequently asked questions
Is 1,5-AG a replacement for HbA1c?
No. HbA1c remains the standard for chronic glycaemic control and diabetes diagnosis. 1,5-AG is complementary — it reveals recent glycaemic excursions that HbA1c can hide.
Do I need to fast?
No fasting required. Continue your usual diet and medications.
When would my doctor order 1,5-AG?
When HbA1c looks acceptable but post-prandial control is in question; when HbA1c is unreliable (haemoglobinopathy, pregnancy, recent transfusion); or in specialised diabetes follow-up. It is not part of routine diabetes care in India.
My 1,5-AG is low. What does that mean?
It usually means your blood glucose has been spiking above ~180 mg/dL in the past 1–2 weeks — typically after meals. Your doctor may adjust meal-time insulin or oral medication, recommend a continuous glucose monitor, or look at dietary patterns. Note — SGLT2 inhibitors lower 1,5-AG independent of glucose.
Does CKD affect this test?
Yes — CKD lowers the renal threshold for glucose, so 1,5-AG falls even without hyperglycaemia. The test becomes unreliable in advanced CKD.
Is 1,5-AG affected by SGLT2 inhibitors?
Yes. SGLT2 inhibitors (empagliflozin, dapagliflozin, canagliflozin) cause glucosuria by lowering the renal threshold for glucose — 1,5-AG falls as a drug effect, independent of glycaemic control. The test cannot be used in patients on SGLT2 inhibitors.
Is this test widely available in India?
No — it is offered in some specialised endocrine centres and reference labs. Discuss availability and clinical utility with your endocrinologist before ordering.
Related Other / Biochemistry tests
Tests commonly ordered alongside 1,5 ANHYDROGLUCITOL, or that help interpret an unexpected result.
Sources & references
- Mayo Clinic Laboratories — 1,5-Anhydroglucitol · accessed 2026-05-30T00:00:00.000Z
- NCBI / PubMed — 1,5-AG as a Glycaemic Marker · accessed 2026-05-30T00:00:00.000Z
- ADA Standards of Care 2024 · accessed 2026-05-30T00:00:00.000Z
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