How is hemoglobin a1c measured

For example, your blood glucose level moves up and down when you eat or exercise. Sickness and stress also can affect your blood glucose test results. The following chart shows how multiple blood glucose measurements over 4 days compare with an A1C measurement. The straight black line shows an A1C measurement of 7. The blue line shows an example of how blood glucose test results might look from self-monitoring four times a day over a 4-day period.

Conditions that change the life span of red blood cells, such as recent blood loss, sickle cell disease , erythropoietin treatment, hemodialysis , or transfusion, can change A1C levels. A falsely high A1C result can occur in people who are very low in iron; for example, those with iron-deficiency anemia.

Other causes of false A1C results include kidney failure or liver disease. People in these groups may have a different type of hemoglobin, known as a hemoglobin variant, which can interfere with some A1C tests.

Most people with a hemoglobin variant have no symptoms and may not know that they carry this type of hemoglobin. Not all A1C tests are unreliable for people with a hemoglobin variant. People with false results from one type of A1C test may need a different type of A1C test to measure their average blood glucose level. The NGSP provides information for health care professionals about which A1C tests are appropriate to use for specific hemoglobin variants. Read about diabetes blood tests for people of African, Mediterranean, or Southeast Asian descent.

Even when the same blood sample is repeatedly measured in the same lab, the results may vary because of small changes in temperature, equipment, or sample handling. Health care professionals understand these variations and repeat lab tests for confirmation. Diabetes develops over time, so even with variations in test results, health care professionals can tell when overall blood glucose levels are becoming too high. When repeated, the A1C test result can be slightly higher or lower than the first measurement.

This means, for example, an A1C reported as 6. Health care professionals can visit www. Your health care professional may use the A1C test to set your treatment goals, modify therapy, and monitor your diabetes management. Experts recommend that people with diabetes have an A1C test at least twice a year.

People will have different A1C targets, depending on their diabetes history and their general health. You should discuss your A1C target with your health care professional. Based on previously published data, the intersubject variability of Hb A 1c 0 is very small approximately 0. Other studies have shown that the relationship between Hb A 1c and AG is strongly linear, but some departures from the regression line are observed 2. Malka et al.

In other words, the slope of the relationship between Hb A 1c and AG is subject specific, or varies from subject to subject as a function of the M RBC. Because the intercept is assumed fixed, it can be obtained using available published data, so it is assumed known.

This suggests that personalized expressions for Hb A 1c as a function of AG can be obtained once an estimate of M RBC is available for that particular individual. The authors suggest that the proposed method explains the nonglycemic variation in Hb A 1c concentration and yields more accurate estimates of Hb A 1c values given AG measurements or vice versa, as a function of the M RBC.

Importantly, the ability to amend Hb A 1c for M RBC in an individual is likely to improve both the diagnostic accuracy of Hb A 1c and its efficacy in predicting diabetic complications. A key assumption of the model is that the M RBC is constant over time within a subject.

This has been demonstrated for up to 5 years, but not over longer periods. Another is that all of the glucose-independent Hb A 1c variation among individuals is assumed to be due to variation in M RBC. If validated, this observation is likely to stimulate investigators to develop simpler and more direct ways to measure M RBC. The final assumption is that k g and Hb A 1c 0 are constant across subjects.

Although these assumptions may be valid biologically, in practice there will be variation in the estimate of the M RBC from one Hb A 1c and AG pair of measures to a different pair obtained from the same subject, and thus the expression for the estimated AG from a given Hb A 1c concentration may also vary depending on which pair of measures is used.

If the model were generalized to allow for random variation in the estimated M RBC , and for other sources of random variation error in the other model components, then more precise estimates of the M RBC and the slope of the Hb A 1c to AG relationship could be obtained by fitting an appropriate regression model.

In addition to the high cost, CGM is technically demanding and patients require extensive training to enable them to use the devices.

This work is likely to generate several follow-up studies. It is important to validate the model by comparing its performance to direct measurements of erythrocyte life span. The model also needs to be evaluated in diverse patient populations; the current study was confined to individuals with type 1 diabetes.

Whether M RBC is a function of observed covariates such as age and sex could be easily addressed by including appropriate interaction terms in a linear model relating AG and Hb A 1c. In addition, it will be valuable to test the model in conditions that alter erythrocyte life span e. After these validation steps are performed, the clinical relevance of this personalized approach i. Ideally, a high-throughput—and inexpensive—assay to measure erythrocyte life span would allow Hb A 1c concentration to be corrected for M RBC , providing a more reliable measure of long-term glycemia.

Unfortunately, this goal is unlikely to be attained in the immediate future. In the interim, the study by Malka et al. Author Contributions: All authors confirmed they have contributed to the intellectual content of this paper and have met the following 3 requirements: a significant contributions to the conception and design, acquisition of data, or analysis and interpretation of data; b drafting or revising the article for intellectual content; and c final approval of the published article.

Authors' Disclosures or Potential Conflicts of Interest: Upon manuscript submission, all authors completed the author disclosure form.

After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes. There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

Your results may mean something different. If you have questions about your results, talk to your health care provider.

Your health care provider may have other recommendations for you, depending on your overall health, age, weight, and other factors. Learn more about laboratory tests, reference ranges, and understanding results. The HbA1c test is not used for gestational diabetes , a type of diabetes that only affects pregnant women, or for diagnosing diabetes in children.

Also, if you have anemia or another type of blood disorder , an HbA1c test may be less accurate for diagnosing diabetes. If you have one of these disorders and are at risk for diabetes, your health care provider may recommend different tests.

The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health. When sugar enters your bloodstream, it attaches to hemoglobin, a protein in your red blood cells. Everybody has some sugar attached to their hemoglobin, but people with higher blood sugar levels have more. The A1C test measures the percentage of your red blood cells that have sugar-coated hemoglobin.

Managing diabetes : If you have diabetes, get an A1C test at least twice a year, more often if your medicine changes or if you have other health conditions. Talk to your doctor about how often is right for you. However, ask your doctor if other tests will be done at the same time and if you need to prepare for them. A normal A1C level is below 5.

Within the 5. Get your A1C tested in addition to—not instead of—regular blood sugar self-testing if you have diabetes.