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Hemoglobin A1C

Understanding hemoglobin A1c (HbA1c) is crucial for managing blood sugar levels and assessing long-term glycemic control. 

Hemoglobin A1c (HbA1c) is a form of hemoglobin that travels through the blood irreversibly bound by glucose. It is formed when glucose attaches to hemoglobin molecules in red blood cells, reflecting average blood sugar levels over the past two to three months.

HbA1c serves as a marker for long-term glycemic control, providing insight into glucose regulation over time. It helps assess the effectiveness of diabetes management strategies and guides treatment decisions.

This article provides comprehensive insights into the definition, function, dietary sources, recommended intake, lab testing, interpretation of results, related biomarkers, and natural ways to support optimal HbA1c levels.

Definition and Function

Definition of Hemoglobin A1c: What is Hemoglobin A1c?  [6., 7.]

Hemoglobin A1c (HbA1c), also referred to as glycated hemoglobin, plays a crucial role in monitoring and managing diabetes mellitus. This compound forms when glucose molecules irreversibly attach to hemoglobin in red blood cells, reflecting the average blood glucose level over the preceding 2 to 3 months. 

As red blood cells have a lifespan of approximately 120 days, the HbA1c test provides a reliable indicator of long-term glycemic control. 

Higher levels of HbA1c (>6.5%) occur in the setting of higher blood sugar levels; therefore, they typically indicate poor blood sugar management and may suggest the presence of diabetes mellitus, while values within the range of 4.0% to 6.0% are considered normal.

Regular monitoring of HbA1c levels is essential for individuals with diabetes to assess the effectiveness of their treatment regimen and adjust it accordingly. 

The American Diabetes Association recommends HbA1c testing at least twice yearly for patients with stable glycemic control, while those with fluctuating blood sugar levels or changes in medication may require testing every three months. 

The significance of HbA1c extends beyond its role in diagnosing and managing diabetes; studies have shown a strong correlation between HbA1c levels and the progression of microvascular complications such as retinopathy, nephropathy, and neuropathy. 

Lower HbA1c levels, particularly in the range of 7% or lower, have been associated with a reduced risk of these complications, highlighting the importance of maintaining optimal blood glucose control.

What is the Significance of HbA1c: What Does HbA1c Mean?  [6., 7.]

Higher levels of hemoglobin A1c (HbA1c) are closely correlated with elevated blood sugar levels over an extended period. Glucose, the primary source of energy for cells, is tightly regulated in the bloodstream by two pancreatic hormones: insulin and glucagon. 

Insulin is secreted in response to rising blood glucose levels and facilitates the uptake of glucose by cells, promoting its conversion into energy or storage as glycogen. In contrast, glucagon is released when blood glucose levels drop, stimulating the liver to release stored glucose into the bloodstream to maintain optimal levels. 

This delicate balance ensures that cells receive a constant supply of glucose for energy production.

When blood sugar levels remain consistently elevated, as indicated by higher HbA1c levels, it can lead to various health complications. 

Prolonged exposure to high blood sugar, known as hyperglycemia, can damage blood vessels and nerves throughout the body. Over time, this damage can result in serious health conditions such as cardiovascular disease, kidney disease, nerve damage, and vision problems. 

Additionally, persistently high blood sugar levels can impair the body's ability to produce insulin or utilize it effectively, exacerbating the condition and potentially leading to the development of type 2 diabetes.

Conversely, insufficient blood sugar, or hypoglycemia, can also pose significant risks to health. When blood sugar levels drop too low, individuals may experience symptoms such as dizziness, confusion, weakness, and even loss of consciousness. 

Severe hypoglycemia can be life-threatening if left untreated. Therefore, maintaining stable blood sugar levels within a healthy range is crucial for overall health and well-being. Regular monitoring of HbA1c levels provides valuable insight into long-term blood sugar control and helps individuals and healthcare providers manage diabetes effectively to prevent complications associated with high blood sugar.

What is the Connection Between HbA1c and Insulin Resistance?

Insulin resistance is a condition where cells in the body become less responsive to the effects of insulin, leading to impaired glucose uptake by the cells. This is a direct cause of elevated blood sugar levels.

It often occurs as a precursor to type 2 diabetes but can also be present in other metabolic disorders. 

The pathogenesis of insulin resistance involves complex interactions between genetic, environmental, and lifestyle factors. 

One of the primary mechanisms is the dysregulation of signaling pathways involved in glucose metabolism, particularly the insulin receptor signaling cascade. When cells become resistant to insulin, they require higher concentrations of insulin to achieve the same glucose uptake, leading to increased insulin production by the pancreas.

As insulin resistance progresses, the pancreas may eventually fail to produce enough insulin to overcome the resistance, resulting in elevated blood glucose levels characteristic of type 2 diabetes. 

This chronic elevation of blood glucose levels contributes to the glycation of hemoglobin, leading to the formation of hemoglobin A1c (HbA1c). HbA1c serves as a marker of long-term glycemic control, reflecting average blood glucose levels over the past two to three months. 

Therefore, in individuals with insulin resistance, the prolonged exposure to elevated blood glucose levels results in higher HbA1c levels, indicating poorer glycemic control.

In addition to insulin resistance that occurs at peripheral tissues like the muscles, fat, and other cells, the liver also develops hepatic insulin resistance.  

Hepatic insulin resistance presents a paradox in type 2 diabetes (T2D), where insulin fails to suppress hepatic glucose production but continues to stimulate lipogenesis, leading to hyperglycemia, hyperlipidemia, and hepatic steatosis.  [14.]

This can cause elevated baseline fasting blood sugar as the liver loses its ability to shut off gluconeogenesis, causing elevations in blood sugar even at night and/or when fasting.  [2.]  This is reflected in a higher HbA1c over time.

What Raises HbA1c?

Anything that causes a persistent or recurring elevation in blood sugar levels will cause HbA1c to rise over time.  

This can include a diet high in carbohydrates, especially simple carbohydrates and sugar, as well as alcohol, and little physical activity.  Stress and poor sleep can also raise blood sugar over time and may impact HbA1c levels.  [10., 13.]

What Foods Raise HbA1c?

Excess energy intake in the form of carbohydrates, in the setting of little to no physical activity, is the ideal setting to raise Hemoglobin A1c levels.  Foods that can cause elevations in blood sugar over time include:

  • Foods high in refined carbohydrates, such as:some text
    • White bread
    • Pasta
    • White rice
    • Sugary cereals
  • Sweetened beverages and fruit juices
  • Processed snacks and desserts containing added sugars, such as:some text
    • Candy
    • Cookies
    • Pastries
    • Ice cream
  • Sugary fruits and dried fruits
  • Starchy vegetables like potatoes and corn
  • High-fat foods that contribute to weight gain, potentially leading to insulin resistance and elevated blood sugar levels

Lab Assessment for HbA1c

General Testing Information/Sample Type

The HbA1c is a simple blood test that requires a blood draw.  While fasting is not required for the HbA1c test, it may be required for other tests commonly co-ordered with the HbA1c test.  

Biomarkers Related to HbA1c

HbA1c is often assessed in context with other biomarkers to provide a more comprehensive assessment of an individual’s cardiometabolic health.  Related blood tests include:

Fasting plasma glucose level: this test measures the amount of glucose in the bloodstream after an overnight fast, typically used to diagnose diabetes or monitor blood sugar control.

Fasting serum insulin levels: a fasting insulin test assesses the amount of insulin present in the blood after an overnight fast, helping to evaluate insulin production and insulin resistance.  Higher insulin levels correlate with a greater degree of insulin resistance.

Insulin resistance indices such as the HOMA-IR: the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) is one index that provides a calculated, quantitative measure of insulin resistance based on fasting glucose and insulin levels.

Lipid profile (e.g., cholesterol, triglycerides): this test evaluates levels of cholesterol, triglycerides, and other lipids in the blood, aiding in the assessment of cardiovascular risk and lipid metabolism.

Inflammatory markers (e.g., hsCRP): high-sensitivity C-reactive protein (hsCRP) is a marker of inflammation in the body, often used to assess cardiovascular risk and monitor inflammatory conditions.

Liver function tests (e.g., ALT, AST): these tests assess liver health by measuring enzymes like alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in the blood, helping to diagnose liver diseases and monitor liver function.  These can be early signs of hepatic insulin resistance. 

Kidney function tests (e.g., creatinine, eGFR): these tests evaluate kidney function by measuring levels of creatinine and estimating glomerular filtration rate (eGFR), important for diagnosing and monitoring kidney diseases.

Red blood cell indices (e.g., mean corpuscular volume, red cell distribution width): red blood cell indices provide information about the size, shape, and number of red blood cells, aiding in the diagnosis and classification of anemia and other blood disorders.

In addition, an oral glucose tolerance test (OGTT) may be ordered.  The oral glucose tolerance test (OGTT) is commonly conducted to assess how well the body processes glucose. It involves drinking a sugary solution, followed by blood tests to measure blood sugar levels at specific intervals, usually over a period of two hours. The test is often used to diagnose prediabetes, diabetes, or gestational diabetes in pregnant women.

Interpreting HbA1c Test Results

Reference Range for HbA1c  [12.]

The hemoglobin A1c reference range is 4.0-5.6% (20-38 mmol/mol).  

Levels between 5.7%-6.4% indicate prediabetes.

AN HbA1c of 6.5% or higher indicates diabetes.  

Clinical Significance of High HbA1c


HbA1c levels falling within the range of 5.7% to 6.4% signifies a state of prediabetes. It indicates a higher than normal average blood glucose concentration over the past 2-3 months, suggesting an increased risk of progressing to overt diabetes if appropriate interventions are not implemented. 

Individuals falling within this range are encouraged to adopt lifestyle modifications such as dietary changes, increased physical activity, and weight management to prevent or delay the onset of diabetes.


Conversely, HbA1c levels exceeding 6.5% are indicative of diabetes mellitus. At this threshold, the risk of microvascular and macrovascular complications associated with diabetes significantly escalates. Chronic hyperglycemia damages blood vessels throughout the body, leading to complications such as retinopathy, neuropathy, nephropathy, and cardiovascular diseases. 

Hence, strict glycemic control is paramount in managing diabetes and preventing the progression of associated complications.

Estimated Average Glucose

The estimated average glucose (eAG) levels derived from HbA1c test results provide clinicians with an additional metric to gauge a patient's average blood glucose concentration over the preceding 2-3 months.  The eAG demonstrates average glucose levels over the last 2-3 months.

However, there exists controversy surrounding the use of eAG due to variations in the conversion formula and discrepancies between eAG and actual glucose levels measured through self-monitoring. Critics argue that reliance solely on eAG may overlook short-term fluctuations in blood glucose levels and fail to capture critical glycemic trends. Additionally, implementing clinical therapies to adjust the eAG did not provide a significant clinical benefit in one study reviewing over 800,000 HbA1c values.  [14.]

Nonalcoholic Hepatic Steatosis  [11.]

Emerging evidence suggests a correlation between rising HbA1c levels and early liver changes indicative of hepatic steatosis. 

Hepatic steatosis, characterized by the accumulation of fat within liver cells, is commonly associated with insulin resistance and metabolic syndrome. 

Elevated HbA1c levels are believed to exacerbate hepatic steatosis by promoting lipogenesis and triglyceride accumulation in the liver, contributing to the pathogenesis of non-alcoholic fatty liver disease (NAFLD). 

Thus, monitoring and managing HbA1c levels not only play a crucial role in glycemic control but also in mitigating the risk of developing hepatic complications associated with metabolic disorders.

Clinical Significance of Low Levels  [9., 16.]

Extremely low levels of hemoglobin A1c (HbA1c) falling below the reference range are uncommon and pose challenges for clinical interpretation. 

While the precise clinical implications of low HbA1c results remain poorly understood, certain conditions such as liver cirrhosis, recent transfusions, and subacute hemorrhage have been associated with such outcomes. 

Low or extremely low HbA1c levels (<5.0% or <4.0%) may also occur in seemingly healthy individuals and are linked to heightened risks of liver diseases, hospitalization, and overall mortality.  [16.]

In non-diabetic patients, an extremely low HbA1c may be a poor prognostic marker.  [3.]

Clinically, it is imperative to investigate the underlying causes of extremely low HbA1c and consider alternative testing or increased health monitoring for patients presenting with such results.

Lab error should also be considered.  

Natural Ways to Optimize HbA1c Levels 


  • Consume a balanced diet rich in whole grains, fruits, vegetables, and lean proteins.
  • Limit intake of processed foods, sugary snacks, and beverages high in added sugars.
  • Monitor carbohydrate intake and focus on complex carbohydrates with a low glycemic index.


  • Engage in regular physical activity such as walking, jogging, swimming, or cycling to help regulate blood sugar levels.
  • Maintain a healthy weight through a combination of diet and exercise.  [8.]
  • Support healthy sleep habits and patterns.  [13.]


  • Chromium: Helps improve insulin sensitivity and glucose metabolism.  [1.]
  • Berberine: berberine has potent hypoglycemic and hypolipidemic effects.  [17.]
  • Alpha-lipoic acid: Acts as an antioxidant and may enhance insulin sensitivity.  [5.]
  • Cinnamon: Contains compounds that mimic insulin and may help lower blood sugar levels.  [4.]

Consult with a healthcare provider before taking any supplements to determine the appropriate dosage and ensure compatibility with existing medications or health conditions.

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Hemoglobin A1C (HbA1c) is a special type of hemoglobin, which is the protein in your red blood cells that helps transport oxygen throughout your body. What sets HbA1c apart is its ability to attach to glucose, the sugar found in your bloodstream. This attachment process creates a record of the average amount of glucose in your blood over the past two to three months, essentially giving a long-term view of your blood sugar levels. Unlike daily glucose tests, which can change based on meals, stress, or exercise, HbA1c offers a wider perspective on how your body handles glucose, an important factor in energy production and overall health.
If Your Levels Are High
Elevated HbA1c levels might mean that your body is struggling to manage the sugar in your blood, which could be due to various reasons like your diet, how much you exercise, stress, or even certain medications. This could also point to specific issues like insulin resistance or metabolic syndrome, where your body has a hard time processing sugar. Additionally, high HbA1c levels could be linked to a higher risk of heart-related problems, since too much sugar in your blood can harm your blood vessels over time. Keep in mind that there are many factors that can affect your blood sugar management, so these conditions are just some possible explanations for higher HbA1c levels.
Symptoms of High Levels
Symptoms of high levels of HbA1c could include frequent urination, increased thirst, fatigue, blurred vision, and unexplained weight loss. However, it's possible to have elevated HbA1c levels without experiencing any noticeable symptoms.
If Your Levels are Low
Low HbA1c levels might mean that your body is doing a great job at managing blood sugar, possibly because of a healthy diet, regular exercise, or effective diabetes control. On the other hand, it could also point to low blood sugar levels, known as hypoglycemia. Some medications, like insulin or certain diabetes drugs, might cause low HbA1c levels. Additionally, issues that affect the lifespan of red blood cells, such as anemia or recent blood loss, could lead to lower HbA1c readings, since the test depends on these cells to accurately show average blood sugar levels over time.
Symptoms of Low Levels
Symptoms of low levels of HbA1c may not be noticeable if the decrease is due to effective glucose management. However, if the cause is hypoglycemia, symptoms could include dizziness, confusion, sweating, hunger, irritability, or heart palpitations. In cases related to conditions affecting red blood cells, symptoms might include fatigue, weakness, or shortness of breath.
See References

[1.] Asbaghi O, Fatemeh N, Mahnaz RK, et al. Effects of chromium supplementation on glycemic control in patients with type 2 diabetes: a systematic review and meta-analysis of randomized controlled trials. Pharmacological Research. 2020;161:105098. doi:

[2.] Basu R, Barosa C, Jones J, Dube S, Carter R, Basu A, Rizza RA. Pathogenesis of prediabetes: role of the liver in isolated fasting hyperglycemia and combined fasting and postprandial hyperglycemia. J Clin Endocrinol Metab. 2013 Mar;98(3):E409-17. doi: 10.1210/jc.2012-3056. Epub 2013 Jan 23. PMID: 23345093; PMCID: PMC3590488.

[3.] Carson AP, Fox CS, McGuire DK, et al. Low Hemoglobin A1c and Risk of All-Cause Mortality Among US Adults Without Diabetes. Circulation: Cardiovascular Quality and Outcomes. 2010;3(6):661-667. doi: 

[4.] Crawford P. Effectiveness of cinnamon for lowering hemoglobin A1C in patients with type 2 diabetes: a randomized, controlled trial. J Am Board Fam Med. 2009 Sep-Oct;22(5):507-12. doi: 10.3122/jabfm.2009.05.080093. PMID: 19734396.

[5.] Elbadawy AM, Abd Elmoniem RO, Elsayed AM. Alpha lipoic acid and diabetes mellitus: potential effects on peripheral neuropathy and different metabolic parameters. Alexandria Journal of Medicine. 2021;57(1):113-120. doi: 

[6.] Eyth E, Naik R. Hemoglobin A1C. [Updated 2023 Mar 13]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: 

[7.] Freeman VS. Glucose and Hemoglobin A1c. Laboratory Medicine. 2014;45(1):e21-e24. doi: 

[8.] Gummesson A, Nyman E, Knutsson M, Karpefors M. Effect of weight reduction on glycated haemoglobin in weight loss trials in patients with type 2 diabetes. Diabetes Obes Metab. 2017 Sep;19(9):1295-1305. doi: 10.1111/dom.12971. Epub 2017 May 22. PMID: 28417575.

[9.] Joob B, Wiwanitkit V. Very low HbA1C, is it a problem? Iran J Pathol. 2018 Summer;13(3):379-380. Epub 2018 Sep 12. PMID: 30636964; PMCID: PMC6322527. 

[10.] Khaw KT . Glycated haemoglobin, diabetes, and mortality in men in Norfolk cohort of European Prospective Investigation of Cancer and Nutrition (EPIC-Norfolk). BMJ. 2001;322(7277):15-15. doi: 

[11.] Masroor M, Haque Z. HbA1C as a Biomarker of Non-alcoholic Fatty Liver Disease: Comparison with Anthropometric Parameters. J Clin Transl Hepatol. 2021 Feb 28;9(1):15-21. doi: 10.14218/JCTH.2019.00046. Epub 2021 Jan 2. PMID: 33604251; PMCID: PMC7868696.

[12.] Pagana KD, Pagana TJ, Pagana TN. Mosby’s Diagnostic & Laboratory Test Reference. 14th ed. St. Louis, Mo: Elsevier; 2019.

[13.] Nakajima H, Kaneita Y, Yokoyama E, Harano S, Tamaki T, Ibuka E, Kaneko A, Takahashi I, Umeda T, Nakaji S, Ohida T. Association between sleep duration and hemoglobin A1c level. Sleep Med. 2008 Oct;9(7):745-52. doi: 10.1016/j.sleep.2007.07.017. Epub 2007 Oct 24. Erratum in: Sleep Med. 2009 Sep;10(8):937-8. PMID: 17921062.

[14.] Samuel VT, Shulman GI. The pathogenesis of insulin resistance: integrating signaling pathways and substrate flux. J Clin Invest. 2016 Jan;126(1):12-22. doi: 10.1172/JCI77812. Epub 2016 Jan 4. PMID: 26727229; PMCID: PMC4701542. 

[15.] Wang D, Chen Y. Usefulness of estimated average glucose (eAG) in glycemic control and cardiovascular risk reduction. Clinical Biochemistry. 2020;84:45-50. doi: 

[16.] Wang P. What Clinical Laboratorians Should Do in Response to Extremely Low Hemoglobin A1c Results. Laboratory Medicine. 2017;48(1):89-92. doi: 

[17.] Yin J, Xing H, Ye J. Efficacy of berberine in patients with type 2 diabetes mellitus. Metabolism. 2008 May;57(5):712-7. doi: 10.1016/j.metabol.2008.01.013. PMID: 18442638; PMCID: PMC2410097.

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