Normal HbA1c Levels and Prediabetes and Diabetes Risk

Last reviewed: May 12, 2026 Last updated: May 12, 2026

Written by: Jay Hastings , CEO of PlexusDx

Jay Hastings is the CEO of PlexusDx, a precision health company focused on genetic testing, blood biomarker insights, and personalized wellness recommendations. He has more than 20 years of experience across healthcare innovation, genomics, laboratory operations, healthcare investing, and strategic finance. His work has included scaling healthcare startups, leading CLIA lab integrations, and helping expand consumer access to precision health tools.

Medically reviewed by: Jayden Lee, PharmD, EMBA

Jayden Lee, PharmD, EMBA, is the PlexusDx Medical Science Liaison with a PharmD and MBA specializing in pharmacogenomics and clinical product development, with a proven ability to bridge the gap between genomic research and practical patient outcomes. Dr. Lee has more than 10 years of professional experience in clinical pharmacy, academia, and research.

This article is part of the PlexusDx Education Hub — your resource for evidence-based guidance on blood testing & biomarkers. Browse all Blood Testing & Biomarkers education

HbA1c is one of the most useful numbers in modern health screening. It reflects your average blood sugar over roughly the past three months, and it is the standard test used to flag prediabetes and diabetes. But two people with the same diet can land on different HbA1c results — and genetics is one reason why. This article explains what HbA1c measures, the thresholds that matter, the named gene variants that influence blood sugar and the test itself, and how pathway-level genetic insight fits in. It is educational and does not diagnose or treat diabetes.

What HbA1c actually measures

Glucose in your blood attaches to hemoglobin, the oxygen-carrying protein in red blood cells. The more glucose circulating over time, the more “glycated” hemoglobin you accumulate. Because red blood cells live about three months, HbA1c gives a rolling average of blood sugar — a steadier picture than a single fasting glucose reading.

The standard HbA1c ranges

Widely used clinical thresholds are: below 5.7% is considered normal, 5.7% to 6.4% falls in the prediabetes range, and 6.5% or higher on repeat testing is used to diagnose diabetes. These cutoffs are set by clinicians and interpreted alongside symptoms and other labs. Only a qualified provider can diagnose prediabetes or diabetes — a single number is never the whole story.

TCF7L2: the strongest common diabetes-risk gene

Of all common genetic variants tied to type 2 diabetes, TCF7L2 has the largest effect. The variant rs7903146 influences insulin secretion from the pancreas, and carriers have a measurably higher lifetime risk of type 2 diabetes across many populations. TCF7L2 does not cause diabetes on its own — it shifts the odds, which lifestyle and body weight then amplify or offset.

FTO, MC4R, and the weight-to-glucose link

Because excess weight strains blood sugar control, genes that influence appetite and body weight indirectly affect HbA1c. FTO (notably rs9939609) and MC4R are among the best-studied. They nudge hunger, satiety, and fat storage, which over years can push glucose regulation in the wrong direction. This is one way genetics and metabolism intersect on your HbA1c report.

Importantly, the effect of these variants is modest and highly modifiable. People carrying higher-risk versions of FTO still respond well to changes in diet and physical activity, and studies show the added risk can be substantially offset by an active lifestyle. Genes influence the starting point; daily habits do much of the work in shaping where HbA1c actually lands.

When genes change the test itself: G6PD and hemoglobin variants

Some genetic differences alter HbA1c without changing your true blood sugar. Because the test depends on red blood cell lifespan, conditions like G6PD deficiency or inherited hemoglobin variants can make HbA1c read falsely high or low. This is why providers sometimes confirm with fasting glucose or a glucose tolerance test, especially when a result does not match the clinical picture.

What the research shows

Large genome-wide studies confirm TCF7L2 as the leading common type 2 diabetes variant, and separate research shows red-cell genetics can shift HbA1c independent of glucose. The consistent lesson is that HbA1c is powerful but not infallible, and diabetes risk is polygenic — many small-effect variants combined with diet, activity, sleep, and weight.

Where pathway-level genetic insight fits

Genetic testing does not diagnose, treat, manage, or prevent diabetes, and it is no replacement for HbA1c testing or a provider’s judgment. What pathway-level insight offers is upstream context about your metabolic biology. The PlexusDx Precision Peptide Genetic Test analyzes 14 pathways, 49 peptides, 150+ genetic insights, mapping systems like glucose regulation and weight metabolism. It tells you about your biology; it does not tell you what to put in your body.

Frequently Asked Questions

What is a normal HbA1c level?

An HbA1c below 5.7% is generally considered normal, 5.7% to 6.4% falls in the prediabetes range, and 6.5% or higher on repeat testing is used to diagnose diabetes. These clinical thresholds are interpreted by a provider alongside your symptoms, fasting glucose, and overall health picture.

Can genetics affect my HbA1c result?

Yes, in two ways. Variants like TCF7L2 (rs7903146) and FTO raise type 2 diabetes risk by affecting insulin and body weight. Separately, red-cell genetics such as G6PD deficiency or hemoglobin variants can make HbA1c read falsely high or low, independent of your actual blood sugar.

Does a genetic test diagnose prediabetes or diabetes?

No. Only blood testing interpreted by a qualified provider — typically HbA1c, fasting glucose, or a glucose tolerance test — can diagnose prediabetes or diabetes. Genetic testing reports pathway-level risk tendencies for education, not a diagnosis, and it cannot treat, manage, or prevent the condition.

What lowers diabetes risk if I carry a risk variant?

Carrying a variant like TCF7L2 shifts odds, not destiny. Research shows diet quality, regular physical activity, weight management, and sleep meaningfully lower type 2 diabetes risk even in higher-risk individuals. Discuss your HbA1c and any genetic context with a qualified provider to build a personalized plan.

Curious about the pathways behind your own biology? The Precision Peptide Genetic Test reads pathway-level genetic signals and translates them into plain-language insight you can bring to a qualified provider. It maps your biology — it does not tell you what to put in your body.

The Precision Peptide Genetic Test analyzes how your genes influence peptide-related biological pathways. It does not recommend, prescribe, or determine which peptides you should use. Consult a qualified healthcare provider before beginning any peptide protocol.

This article is part of the PlexusDx Education Hub. Browse all Blood Testing & Biomarkers education

Medical and Editorial Standards

Medical review process: This article was reviewed for medical accuracy, scientific clarity, evidence alignment, and appropriate discussion of genetics, medications, supplements, biomarkers, and health-related claims.

Sources and evidence: PlexusDx educational content is developed using peer-reviewed research, clinical literature, reputable medical references, and, where applicable, public health or regulatory guidance. References are included at the end of the article when scientific, medical, or health-related claims are discussed.

Commercial transparency: PlexusDx offers genetic testing, blood biomarker testing, personalized supplement recommendations, and related precision wellness services. Product mentions are intended to help readers understand available options and should not be interpreted as medical advice.

Important disclaimer: PlexusDx educational content is for informational purposes only and should not be used as a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making decisions about medications, supplements, genetic testing, lab testing, or health-related care.