Does an abnormal HbA1c always mean diabetes?

HbA1c always comes when Diabetes diagnosis and/or Diabetes control is under consideration. However, one must be very cautious, as HBa1c readings can be misleading in a variety of other medical conditions. So it is advisable to talk to your doctor before making any decision related to your health based solely on HbA1c value.

The simple answer to the topic of today’s discussion,” Does an abnormal HbA1c always mean diabetes is “NO”

An elevated HbA1c in someone who does not have diabetes can occur for two broad reasons:

1. True increases in average blood glucose (prediabetes or other causes of hyperglycemia).
2. Falsely elevated HbA1c due to conditions that alter red blood cell lifespan or interfere with the assay.

1. Conditions causing genuinely higher glucose levels

Prediabetes

• Most common cause.
• HbA1c 5.7–6.4% suggests increased diabetes risk.
• Confirm with fasting plasma glucose or an oral glucose tolerance test.

Stress hyperglycemia

Can occur with:

• Severe infections
• Surgery
• Trauma
• Acute myocardial infarction
• Stroke

Endocrine disorders

• Cushing syndrome
• Acromegaly
• Pheochromocytoma
• Hyperthyroidism

Medications

Examples include:

• Glucocorticoids
• Certain antipsychotics (e.g., olanzapine)
• Some antiretroviral therapies
• Tacrolimus and cyclosporine
• Thiazide diuretics (occasionally)

---

2. Falsely elevated HbA1c

HbA1c reflects glycation over the lifespan of erythrocytes (approximately 120 days). Conditions that prolong red cell survival may increase HbA1c despite normal glucose levels.

Iron deficiency anemia

• One of the commonest causes of falsely elevated HbA1c.
• HbA1c often decreases after iron replacement.

Vitamin B12 deficiency

• Reduced erythropoiesis and prolonged RBC survival can increase HbA1c.

Folate deficiency

• Similar mechanism to B12 deficiency.

Asplenia or splenectomy

• Reduced removal of aging erythrocytes.

Chronic kidney disease

May affect HbA1c unpredictably:

• Advanced CKD often lowers HbA1c because of shortened RBC survival.
• However, carbamylated hemoglobin and certain assay methods may occasionally give higher results.

Severe hyperbilirubinemia

• Can interfere with some laboratory methods.

Severe hypertriglyceridemia

• May interfere with some assays.

Alcoholism

• Formation of acetaldehyde-hemoglobin compounds may influence certain assays.

Chronic opioid use

• Rarely associated with assay interference.

Hemoglobin variants

Examples include:

• Sickle cell disease
• Hemoglobin C trait
• Hemoglobin E trait

Depending on the assay used, these variants can cause either falsely high or falsely low HbA1c values.

---

When to suspect a falsely elevated HbA1c

Consider this when:

• HbA1c does not correlate with fasting or random glucose values.
• HbA1c is elevated but continuous glucose monitoring (CGM) or self-monitoring shows normal glucose patterns.
• There is known anemia, hemoglobinopathy, recent transfusion, or another condition affecting RBC turnover.

---

Recommended evaluation

If a person without known diabetes has an unexpectedly high HbA1c:

1. Repeat the HbA1c using an NGSP-certified method.
2. Check:
   • Fasting plasma glucose.
   • Consider a 75-g oral glucose tolerance test if uncertainty remains.
3. Review medications.
4. Order:
   • CBC.
   • Ferritin and iron studies.
   • Vitamin B12 and folate levels.
   • Renal function tests.
5. Consider hemoglobin electrophoresis if there is suspicion of a hemoglobin variant.

---

Practical interpretation

HbA1c	Interpretation
<5.7%	Usually normal
5.7–6.4%	Prediabetes (if confirmed)
≥6.5%	Diabetes if confirmed by repeat testing or another diagnostic test

An isolated elevated HbA1c should not automatically be interpreted as diabetes, especially when the clinical picture and measured glucose values are inconsistent with the result. Confirmatory testing is often necessary.

For Common Signs of Anemia, Visit; https://drsuhailmarfani.com/2026/06/15/common-signs-of-anemia-low-hemoglobin-when-should-you-worry/

Author: Dr. Suhail Marfani
Specialist in Internal Medicine and Diabetes Doctor
Prime Medical Center, Al-Qasimia Branch
Sharjah, United Arab Emirates