At what A1C level does damage start?

Harvard Health Blog

• By Monique Tello, MD, MPH, Contributor

"Treat the patient, not the number." This is a very old and sound medical school teaching. However, when it comes to blood sugar control in diabetes, we have tended to treat the number, thinking that a lower number would equal better health.

Uncontrolled type 2 diabetes (also known as adult-onset diabetes) is associated with all sorts of very bad things: infections, angry nerve endings causing chronic pain, damaged kidneys, vision loss and blindness, blocked arteries causing heart attacks, strokes, and amputations… So of course, it made good sense that the lower the blood sugar, the lower the chances of bad things happening to our patients.

One easy, accurate way for us to measure a person’s blood sugar over time is the hemoglobin A1c (HbA1c) level, which is basically the amount of sugar stuck to the hemoglobin molecules inside of our blood cells. These cells last for about three months, so, the A1c is thought of as a measure of blood sugars over the prior three months.

Generally, clinical guidelines have recommended an A1c goal of less than 7% for most people (not necessarily including the elderly or very ill), with a lower goal — closer to normal, or under 6.5% — for younger people.

We as doctors were supposed to first encourage diet and exercise, all that good lifestyle change stuff, which is very well studied and shown to decrease blood sugars significantly. But if patients didn’t meet those target A1c levels with diet and exercise alone, then per standard guidelines, the next step was to add medications, starting with pills. If the levels still weren’t at goal, then it was time to start insulin injections.

While all this sounds very orderly and clinically rational, in practice it hasn’t worked very well. I have seen firsthand how enthusiastic attention to the A1c can be helpful as well as harmful for patients.

And so have experts from the Clinical Guidelines Committee of the American College of Physicians, a well-established academic medical organization. They examined findings from four large diabetes studies that included almost 30,000 people, and made four very important (and welcome!) new guidelines around blood sugar control. Here’s the big picture.

Blood sugar goals should take into account a patient’s life expectancy and general health, as well as personal preferences, and include a frank discussion of the risks, benefits, and costs of medications. This is a big deal because it reflects a change in how we think about blood sugar control. It’s not a simply number to aim for; it’s a discussion. Diabetes medications have many potential side effects, including dangerously low blood sugar (hypoglycemia) and weight gain (insulin can cause substantial weight gain). Yes, uncontrolled blood sugars can lead to very bad things, but patients should get all the information they need to balance the risks and benefits of any blood sugar control plan.

…though if lifestyle changes can get that number lower, then go for it. For patients who want to live a long and healthy life and try to avoid the complications of diabetes, they will need to keep their blood sugars as normal as possible — that means an A1c under 6.5%. However, studies show that using medications to achieve that goal significantly increases the risk of harmful side effects like hypoglycemia and weight gain. To live longer and healthier and avoid both the complications of diabetes as well as the risks of medications, there’s this amazing thing called lifestyle change. This involves exercise, healthy diet, weight loss, and not smoking. It is very effective. Lifestyle change also can help achieve healthy blood pressure and cholesterol levels, which in turn reduce the risk for heart disease. And heart disease is a serious and common complication of diabetes.

Lifestyle change should be the cornerstone of treatment for type 2 diabetes. The recommendations go on to say that for patients who achieve an A1c below 6.5% with medications, we should decrease or even discontinue those drugs. Doing so requires careful monitoring to ensure that the person stays at the goal set with his or her doctor, which should be no lower than 7%, for the reasons stated above.

Elderly patients, and those with serious medical conditions, will benefit from simply controlling the symptoms they have from high blood sugars, like frequent urination and incontinence, rather than aiming for any particular A1c level. Who would be included in this group? People with a life expectancy of less than 10 years, or those who have advanced forms of dementia, emphysema, or cancer; or end-stage kidney, liver, or heart failure. There is little to no evidence for any meaningful benefit of intervening to achieve a target A1c in these populations; there is plenty of evidence for harm. In particular, diabetes medications can cause low blood sugars, leading to weakness, dizziness, and falls. There is the added consideration that elderly and sick patients often end up on a long list of medications that can (and do) interact, causing even more side effects.

There is no question that type 2 diabetes needs to be taken seriously and treated. But common sense should rule the day. Lifestyle changes are very effective, and the side effects of eating more healthfully and staying more active are positive ones. Every person with type 2 diabetes is an individual. No single goal is right for everyone, and each patient should have a say in how to manage their blood sugars and manage risk. That means an informed discussion, and thoughtful consideration to the number.

Hemoglobin A1c targets for glycemic control with pharmacologic therapy for nonpregnant adults with type 2 diabetes mellitus: A guidance statement update from the American College of Physicians. Annals of Internal Medicine, March 2018.

An overview of the management of diabetes in non-pregnant adults. MGH Primary Care Office Insite, updated June 2016.

Management of persistent hyperglycemia in type 2 diabetes mellitus. UpToDate, updated April 2017.

Monique Tello, MD, MPH, Contributor

Dr. Monique Tello is a practicing physician at Massachusetts General Hospital, director of research and academic affairs for the MGH DGM Healthy Lifestyle Program, clinical instructor at Harvard Medical School, and author of the evidence-based lifestyle … See Full Bio

As a service to our readers, Harvard Health Publishing provides access to our library of archived content. Please note the date of last review or update on all articles.

No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.

Commenting has been closed for this post.

Get the latest in health news delivered to your inbox!

If your blood sugar levels have remained stable and your A1C is within your target range, the American Diabetes Association (ADA) recommends getting the test two times a year. If your therapy has changed or you are not meeting your blood sugar targets, the ADA recommends getting the test four times per year. This simple blood draw can be done in your doctor’s office.

The A1C test results provide insight into how your treatment plan is working and how it might be modified to better control the condition. Often, your blood sample is sent out to a lab, though some doctors can use a point-of-care A1C test, where a finger stick can be done in the office, with results available in about 10 minutes.

While in-office tests can be used to monitor the disease, the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) notes that most point-of-care tests should not be used for diagnosis. That can only be done by lab tests certified by the NGSP, an organization that standardizes A1C test results. Any in-office test results pointing to a change in your health should be confirmed by conventional lab tests.

What Do Your A1C Results Mean?

The A1C test measures the glucose (blood sugar) in your blood by assessing the amount of what’s called glycated hemoglobin. “Hemoglobin is a protein within red blood cells. As glucose enters the bloodstream, it binds to hemoglobin. The more glucose that enters the bloodstream, the higher the amount of glycated hemoglobin,” Dr. Dodell says.

According to the ADA, an A1C level below 5.7 percent is considered normal; between 5.7 and 6.4 signals prediabetes; and over 6.5 percent indicates type 2 diabetes. For many people with type 2 diabetes, the goal is to reduce A1C levels.

Your A1C goal is specific to you. Several factors come into play, such as your age, how advanced the diabetes is, and whether you have any other health conditions. If you can keep your A1C number below your goal — which, for many people with diabetes, is less than 7 percent, says Dodell — you can reduce the risk of complications, such as nerve damage and eye problems.

What Are Some Top Tips for Lowering A1C?

Your A1C score is a helpful tool, Dodell says, but it is not the only indicator of how healthy you are.

For example, you could hit your A1C goal but still have wide fluctuations in your blood sugar levels, which is more common among people who take insulin. You’ll need to bring these day-to-day fluctuations under control, since they can lower your quality of life and increase your risk of complications, he says.

Think of your diabetes as you would a job, Dodell says. It takes work, but the time and effort you put into it can result in good control and an improved quality of life. “The key to reaching your A1C goal is trying to follow a healthy lifestyle,” he says.

Making these changes can help you improve your day-to-day blood sugar management and lower your A1C.

1. Start an Exercise Plan You Enjoy, and Do It Regularly

Find something you enjoy doing that gets your body moving, whether it’s taking your dog for a walk, playing a sport with a friend, or riding your bike.

The ADA recommends getting 150 minutes of moderate exercise per week, says Jordana Turkel, a certified diabetes care and education specialist (CDCES) and registered dietitian at Park Avenue Endocrinology & Nutrition in New York City. Different types of exercise (both strength or resistance training and aerobic exercise) can lower your A1C by making your body more sensitive to insulin, Turkel says. She encourages her patients not to go more than two days in a row without exercising and to aim for two days of strength training per week.

Be sure to check with your healthcare provider before embarking on an exercise plan, though. Together, you can come up with an individualized plan.

And if you monitor your blood sugar daily, check it before and after exercise. As the ADA explains, exercise improves insulin sensitivity and lowers your blood sugar levels. In certain circumstances, though, stress hormones produced during more intense exercise can also increase blood sugar levels. In addition, other factors, such as what you eat before exercise and the timing of your workout, may also affect your numbers.

2. Eat a Balanced Diet With Proper Portion Sizes

It’s best to check with a CDCES or registered dietitian/nutritionist to determine what a balanced diet and appropriate portion sizes mean for you. But a great rule of thumb is to fill half of your plate with veggies, a quarter with protein, and a quarter with whole grains, says Turkel. If you like fruit, limit your portion to a small cup, eaten with a little protein or lean fat to help you digest the carbohydrates in a way that is less likely to spike your blood sugar.

Also, avoid processed foods as much as possible, and try to avoid sugary sodas and fruit juice, which are high in carbs and calories, and thus can lead to spikes in blood sugar and contribute to weight gain, according to the ADA.

3. Stick to a Regular Schedule, So You Can More Easily Follow a Healthy Diet 

Skipping meals, letting too much time pass between meals, or eating too much or too often can cause your blood sugar levels to fall and rise too much, Cleveland Clinic points out. This is especially true if you are taking insulin or certain other diabetes drugs. Your doctor can help you determine the best meal schedule for your lifestyle.

4. Follow the Diabetes Treatment Plan Your Healthcare Team Recommends

Diabetes treatment is very individualized, noted a February 2022 article in Diabetes, Metabolic Syndrome and Obesity: Targets and Therapy. After all, factors including how long you’ve lived with the disease, your socioeconomic status, and any other conditions you’re living with can play a role in the best treatment approach for you.

Your healthcare team will help you determine which steps to take to successfully manage diabetes. Always talk to your doctor before making any changes, such as starting a diet very low in carbohydrates or beginning a new exercise regimen. This is especially important before making any medication or insulin changes.

5. Check Your Blood Sugar Levels as Your Doctor Has Directed

Work with your doctor to determine if you should check your blood sugar — and how often. You may be tempted to pick up an A1C home testing kit, but Dodell says having your A1C checked by your doctor every three to six months is sufficient. A better idea is to use a continuous glucose monitor. He recommends checking your “time in range” to see if you are at the optimal level. For many people that is 70 to 180 milligrams per deciliter (3.9 to 10 millimoles per liter), according to ADA guidelines.

Understanding your A1C levels is an important part of your overall diabetes management. If you have any questions about your A1C or what it means, don’t hesitate to ask your doctor.

Additional reporting by Mikel Theobald