1,5-Anhydroglucitol (GlycoMark®)

Introduction

In the realm of functional medicine and metabolic health, precise biomarkers are critical to detecting imbalances and preventing chronic disease. One such underutilized yet powerful marker is 1,5-Anhydroglucitol (1,5-AG), most commonly assessed via the GlycoMark® test. Unlike traditional long-term markers like HbA1C, 1,5-AG reflects short-term glycemic excursions—key in identifying early or hidden glycemic dysregulation. As a Nurse Practitioner with autonomous practice authority in Florida, I emphasize this marker when guiding patient-centered metabolic care.

Background of 1,5-Anhydroglucitol

1,5-AG is a naturally occurring monosaccharide found in the diet and filtered by the kidneys. Under euglycemic conditions, it is efficiently reabsorbed. However, when blood glucose levels exceed 160–180 mg/dL, glucose saturates the renal tubules, outcompeting 1,5-AG and causing its urinary loss—thereby lowering serum levels.

This mechanism makes 1,5-AG an excellent marker for postprandial hyperglycemia and glycemic variability—which are not always captured by Hemoglobin A1C.

What Does the GlycoMark® Test Measure?

The GlycoMark® test quantifies circulating 1,5-AG levels in the blood. Unlike HbA1C, which reflects glycemic trends over 2–3 months, GlycoMark® indicates short-term fluctuations over the prior 1–2 weeks—particularly after meals. This test is particularly useful in Dysglycemia and Insulin Resistance evaluation.

Interpreting 1,5-AG Levels

Standard and Optimal Ranges

• Standard Range: 7.30 – 36.60 µg/mL
  
• Optimal Range: 24.00 – 36.60 µg/mL

   

Clinical Implications of Low 1,5-AG Levels

Low levels (typically <10 µg/mL) suggest frequent hyperglycemia above renal thresholds, often missed by A1C. These values are associated with:

• Type 2 Diabetes: Early detection of postprandial spikes
  
• Cardiovascular Risk: Levels <6 µg/mL linked to increased risk of heart failure, stroke, and coronary artery disease
  
• Cancer Risk in Men: Emerging studies show associations in non-diabetic men
  
• Type 1 Diabetes: Levels as low as 3.8 µg/mL correlate with severe glycemic variability, despite “normal” average glucose levels

   

Clinical Implications of High 1,5-AG Levels

High 1,5-AG levels (above 36.60 µg/mL) currently have no known pathological significance, but clinical context remains essential.

Factors That Affect 1,5-AG Levels

Falsely Decreased

• Carbohydrate-restricted diets
  
• Prolonged fasting or NPO status
  
• Use of SGLT2 inhibitors (e.g., INVOKANA®), which block glucose and 1,5-AG reabsorption
  
• Steroid therapy

   

Falsely Elevated

• Certain Chinese herbs (e.g., Polygala tenuifolia, senega syrup)

   

Drug Associations

• Decreased 1,5-AG: SGLT2 inhibitors (e.g., canagliflozin), corticosteroids
  
• Increased 1,5-AG: Rare; possibly herbal agents only

   

Related Biomarkers

A full glycemic panel should include:

• Fasting Glucose
  
• Fasting Insulin
  
• C-Peptide
  
• eAG (Estimated Average Glucose)
  
• Fructosamine
  
• QUICKI
  
• HOMA2-IR and HOMA2-%B

   

Clinical Application in Functional Medicine

In functional medicine, 1,5-AG reflects cellular glucose handling in real time. It is especially useful for:

• Uncovering hidden hyperglycemia
  
• Monitoring Metabolic Syndrome
  
• Fine-tuning dietary and pharmacologic interventions
  
• Identifying at-risk patients before conventional lab values shift

   

Monitoring Therapeutic Response

1,5-AG allows real-time monitoring of:

• Glycemic control in response to medication or dietary change
  
• Postprandial glucose surges in insulin-resistant individuals
  
• Effectiveness of SGLT2 inhibitors or ketogenic interventions

   

Guiding Personalized Care

Understanding a patient’s 1,5-AG levels supports:

• Adjustments to carbohydrate intake
  
• Detection of non-adherence to glucose control therapies
  
• Justification for CGM (Continuous Glucose Monitoring) referral
• Enhanced prevention of Diabetic Complications

Conclusion

The GlycoMark® test for 1,5-Anhydroglucitol is a sensitive, functional biomarker of glycemic variability and postprandial spikes. Especially in patients with borderline HbA1C or unexplained symptoms, this marker can uncover hidden dysregulation and guide timely intervention. When used alongside other biomarkers and clinical insights, it empowers practitioners to deliver personalized, root-cause-focused care.

Relevant Articles and Resources

• Dungan, K. M., Buse, J. B., Largay, J., Kelly, M., Button, E., Wittlin, S., & English, J. (2015). 1,5-anhydroglucitol as a useful marker for assessing short-term glycemic control in type 1 diabetes. Diabetes Technology & Therapeutics, 17(3), 169-176. https://pmc.ncbi.nlm.nih.gov/articles/PMC4411548/

• Yamanouchi, T., Kawai, K., & Yoshida, M. (1996). Clinical usefulness of serum 1,5-anhydroglucitol in monitoring glycemia in non-insulin-dependent diabetes mellitus. Diabetes Research and Clinical Practice, 31(2-3), 123-130. https://pubmed.ncbi.nlm.nih.gov/8684103/

• Dungan, K. M., Buse, J. B., Largay, J., Kelly, M., Button, E., Wittlin, S., & English, J. (2014). Evaluation of 1,5-anhydroglucitol, hemoglobin A1c, and glucose levels in youth and adults with diabetes. Diabetes Care, 37(10), 2747-2753. https://pmc.ncbi.nlm.nih.gov/articles/PMC3767297/

• Selvin, E., Rawlings, A. M., Lutsey, P. L., Maruthur, N., Steffes, M. W., Coresh, J., & Pankow, J. S. (2019). Response of 1,5-anhydroglucitol level to intensive glucose-lowering intervention and association with clinical outcomes in type 2 diabetes: The ADVANCE trial. Diabetes Care, 42(9), 1742-1748. https://pubmed.ncbi.nlm.nih.gov/31050156/