Can dehydration affect Hemoglobin A1c (Hgb A1c) results?

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From the Guidelines

Dehydration can indeed affect Hemoglobin A1c (HbA1c) results, typically causing falsely elevated readings. When a person is dehydrated, the concentration of red blood cells in the bloodstream increases relative to plasma volume, creating a state of hemoconcentration. Since HbA1c measures the percentage of hemoglobin molecules with glucose attached, this concentration effect can make the percentage appear higher than it would be in a properly hydrated state. The effect is generally modest but can be clinically significant, potentially leading to overestimation of average blood glucose levels by 0.5-1.0 percentage points in cases of significant dehydration.

This is particularly important for patients with diabetes who may experience dehydration due to high blood glucose levels or certain medications like diuretics 1. To ensure accurate HbA1c results, patients should maintain normal hydration before testing, especially if they have conditions that predispose them to fluid imbalances. Healthcare providers should consider hydration status when interpreting borderline HbA1c results, particularly when making treatment decisions or diagnosing diabetes.

Some key points to consider include:

  • Dehydration can lead to hemoconcentration, which affects HbA1c results
  • Patients with diabetes are at higher risk of dehydration due to various factors
  • Accurate HbA1c results rely on proper hydration status
  • Healthcare providers should take hydration status into account when interpreting HbA1c results, as seen in recent guidelines 1.

In clinical practice, it is essential to prioritize the patient's hydration status to ensure accurate HbA1c results and make informed treatment decisions, as highlighted in the most recent study 1.

From the Research

Dehydration and Hgb A1c Results

  • There is no direct evidence in the provided studies that dehydration alters Hemoglobin A1c (Hgb A1c) results 2, 3, 4, 5, 6.
  • However, it is essential to note that Hgb A1c measurements can be affected by various factors, including hemoglobin variants 2, hemolytic anemia 5, and liver cirrhosis 5.
  • In patients with certain conditions, such as hereditary hemolytic anemia and liver cirrhosis, Hgb A1c and glycated albumin (GA) may be unreliable, and estimated Hgb A1c calculated from average glucose levels may be useful for evaluating glycemic control 5.
  • The provided studies focus on the limitations of Hgb A1c measurements, the importance of average glucose levels, and the role of continuous glucose monitoring in diabetes management 3, 4, 5, 6.
  • Dehydration is not explicitly mentioned as a factor that affects Hgb A1c results in the provided studies.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Led Astray by Hemoglobin A1c: A Case of Misdiagnosis of Diabetes by Falsely Elevated Hemoglobin A1c.

Journal of investigative medicine high impact case reports, 2016

Research

The correlation of hemoglobin A1c to blood glucose.

Journal of diabetes science and technology, 2009

Research

A View Beyond HbA1c: Role of Continuous Glucose Monitoring.

Diabetes therapy : research, treatment and education of diabetes and related disorders, 2019

Research

Pitfalls in hemoglobin A1c measurement: when results may be misleading.

Journal of general internal medicine, 2014

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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