How to lower A1C, and how long it takes

How long it takes

A1C reflects sugar stuck to hemoglobin over the life of your red blood cells, about three months. New cells made after you change your habits replace old ones gradually, so the number drifts down over weeks and settles after about three months.

That is why most clinicians recheck A1C about three months after a change. Daily glucose checks or a CGM show progress sooner. A two-week drop in CGM average can show up as a GMI change before your lab A1C catches up; see GMI vs A1C.

Steps with good evidence

1. Build meals around fiber. In a 2020 PLoS Medicine review of trials in people with diabetes, eating more fiber lowered A1C modestly and improved cholesterol and weight. Vegetables, legumes, whole fruit and whole grains are the best sources. See foods that lower A1C.
2. Use the plate method. NIDDK suggests half the plate nonstarchy vegetables, a quarter high-fiber carbs such as beans or whole grains, and a quarter protein, with water on the side.
3. Cut sugary drinks and sweets. Soda, juice, sweetened coffee drinks, cookies and cakes raise blood sugar fast.
4. Move at least 150 minutes a week. About 30 minutes of brisk walking on most days, plus strength training twice a week. Short sessions count.
5. Lose 5% to 7% of body weight if you carry extra. NIDDK says this much can help manage blood glucose, cholesterol and blood pressure.
6. Sleep 7 to 8 hours and manage stress. Both affect blood sugar.
7. Take medicines as prescribed. Don't skip or ration doses because of cost; tell your clinician so they can find an option you can afford.

If you have prediabetes

The NIH Diabetes Prevention Program is the best evidence that lifestyle change works. People with high risk who aimed to lose 7% of body weight and exercise about 150 minutes a week cut their risk of developing type 2 diabetes by 58% over about three years, and by 71% at ages 60 and older. The benefit lasted at least 15 years in follow-up.

Lifestyle change lowers risk; it does not promise that diabetes will never develop. Keep testing on the schedule your clinician sets.

When medicine is part of the plan

Many people need medicine as well as lifestyle changes to reach their goal, and that is not a failure. Your clinician decides which medicine fits, based on your A1C, other conditions and cost. Keep the lifestyle steps going alongside it.

Lowering A1C quickly with medicine can cause low blood sugar. Get help for shaking, sweating, confusion or a reading below 70 mg/dL. Seek care for symptoms of very high blood sugar or ketones in your urine.

Make sure the number is real

Iron deficiency can push A1C up, and blood loss, kidney or liver disease and hemoglobin variants can distort it. If your A1C doesn't fit your glucose readings, ask about ferritin, a CBC or a different glucose test before changing treatment.