1,5-Anhydroglucitol
Also known as: 1,5-AG, GlycoMark
What Does 1,5-Anhydroglucitol Measure?
1,5-Anhydroglucitol (1,5-AG) is a naturally occurring glucose-like compound found in virtually all foods and circulating in the bloodstream. Unlike glucose, 1,5-AG is not produced by the body in significant amounts — it is absorbed from dietary sources and maintained at a relatively stable concentration in healthy individuals. The test measures the blood level of this compound as a short-term indicator of glucose control, specifically reflecting glucose spikes that occurred over the past 1–2 weeks.
Why Does 1,5-Anhydroglucitol Matter?
1,5-AG is a sensitive marker for detecting postprandial (after-meal) glucose excursions, even when other markers like HbA1c appear normal. When blood glucose rises above the renal threshold (approximately 180 mg/dL), excess glucose competes with 1,5-AG for reabsorption in the kidneys, causing 1,5-AG to be lost in the urine. This results in a rapid drop in serum 1,5-AG levels. Because it responds quickly to glucose fluctuations, 1,5-AG is especially valuable for monitoring short-term glycemic control in people with diabetes, identifying patients who may have frequent glucose spikes despite acceptable average glucose readings, and assessing the effectiveness of diabetes treatment changes.
Normal Ranges
Males
≥ 14.0 µg/mL (values below 10 µg/mL suggest poor glycemic control)
Females
≥ 10.7 µg/mL (slightly lower reference range due to hormonal differences; values below 6 µg/mL suggest poor glycemic control)
Children
Varies by age; generally similar to adult ranges but less standardized — consult age-specific reference intervals
Causes of High Levels
- Well-controlled blood glucose with no significant hyperglycemic episodes
- No diabetes or prediabetes (normal glucose metabolism)
- Effective diabetes management with medications or lifestyle interventions
- High dietary intake of 1,5-AG-rich foods (e.g., grains, legumes) in healthy individuals
- Renal impairment that reduces urinary excretion of 1,5-AG (falsely elevated result)
Causes of Low Levels
- Frequent postprandial glucose spikes exceeding 180 mg/dL
- Poorly controlled type 1 or type 2 diabetes
- Gestational diabetes with uncontrolled glucose levels
- Use of SGLT2 inhibitors (e.g., empagliflozin, dapagliflozin) which cause glucose and 1,5-AG to be excreted in urine, leading to falsely low readings
How to Improve Your 1,5-Anhydroglucitol
Diet
- Reduce consumption of refined carbohydrates and added sugars to prevent glucose spikes above 180 mg/dL
- Focus on low-glycemic index foods such as legumes, non-starchy vegetables, and whole grains to blunt postprandial glucose rises
- Eat smaller, more frequent meals to minimize large glucose excursions after eating
- Increase dietary fiber intake (25–38 g/day) from vegetables, fruits, and whole grains to slow glucose absorption
- Pair carbohydrates with protein or healthy fats to reduce the speed of glucose entry into the bloodstream
Supplements
- Berberine (500 mg, 2–3 times daily with meals) has been shown to reduce postprandial glucose spikes
- Alpha-lipoic acid (600–1200 mg/day) may improve insulin sensitivity and reduce glucose excursions
- Magnesium (200–400 mg/day) supports insulin function and glucose metabolism, particularly if deficient
- Chromium picolinate (200–1000 mcg/day) may help improve glucose tolerance and reduce spikes
- Psyllium husk (5–10 g before meals) slows carbohydrate absorption and reduces postprandial glucose elevations
Related Biomarkers
Frequently Asked Questions
What is the difference between 1,5-AG and HbA1c?
HbA1c reflects average blood glucose over the past 2–3 months, making it useful for long-term diabetes management but slow to detect recent changes. 1,5-AG, in contrast, captures glucose control over just the past 1–2 weeks and is particularly sensitive to short-term glucose spikes. A patient could have a normal HbA1c but still have frequent high glucose spikes after meals — something 1,5-AG is better equipped to detect. Together, both tests provide a more complete picture of glycemic control.
Can I use 1,5-AG to diagnose diabetes?
No, 1,5-AG is not a diagnostic test for diabetes. It is used to monitor glycemic control in people already known to have diabetes or prediabetes. Diagnosis of diabetes relies on fasting glucose, oral glucose tolerance tests, or HbA1c values confirmed on repeat testing. However, a low 1,5-AG in someone not yet diagnosed with diabetes may warrant further investigation.
Why does taking an SGLT2 inhibitor affect my 1,5-AG results?
SGLT2 inhibitors (such as empagliflozin, dapagliflozin, and canagliflozin) work by causing the kidneys to excrete excess glucose into the urine. Unfortunately, this same mechanism also causes 1,5-AG to be lost in the urine, leading to artificially low 1,5-AG levels even when blood glucose is well-controlled. This means 1,5-AG is not a reliable marker for monitoring glycemic control in patients on SGLT2 inhibitors, and other tests like HbA1c or fructosamine should be used instead.
How quickly does 1,5-AG respond to changes in blood sugar control?
1,5-AG is one of the fastest-responding biomarkers of glucose control. When blood glucose is well-controlled and not exceeding the renal threshold (about 180 mg/dL), 1,5-AG levels can normalize within approximately 1–2 weeks. Conversely, when frequent glucose spikes occur, 1,5-AG levels drop rapidly within days. This makes it an excellent tool for tracking the near-term impact of medication adjustments, diet changes, or new exercise habits.