You can lower your A1C by changing what you eat, how you move, how you sleep, and in many cases, by working with your doctor on medication. A1C measures the percentage of your red blood cells that have sugar permanently attached to them, and since red blood cells live about 120 days, your A1C reflects a weighted average of your blood sugar over the previous two to three months. That timeline matters: any change you make today won’t fully show up on your next test for roughly eight to twelve weeks.
For reference, a normal A1C is below 5.7%, prediabetes falls between 5.7% and 6.4%, and 6.5% or above indicates diabetes.
Why A1C Takes Months to Change
Sugar in your bloodstream binds to hemoglobin, the oxygen-carrying protein inside red blood cells. This bond is permanent for the life of that cell. Because your body constantly produces new red blood cells and retires old ones on a roughly 120-day cycle, your A1C at any given moment is a rolling snapshot. The most recent four to six weeks carry the most weight, since more of those red blood cells are still circulating. So if you start making changes now, you’ll see some movement at your next test, but the full effect takes a couple of cycles to show up.
Most people get their A1C tested at least twice a year when things are stable. If you’ve recently changed your diet, started a new medication, or adjusted your routine, your doctor will likely recheck at three months to see how you’re responding.
Shift What You Eat, Not Just How Much
The single most impactful dietary change for A1C is reducing how quickly your meals raise blood sugar. A large meta-analysis of randomized controlled trials found that switching to lower-glycemic foods reduced A1C by an average of 0.31 percentage points compared to higher-glycemic diets. That may sound modest, but for someone sitting at 7.0%, dropping to 6.7% is clinically meaningful, and diet changes stack with other interventions.
In practical terms, this means swapping refined grains for whole grains, choosing steel-cut oats over instant, eating whole fruit instead of drinking juice, and pairing carbohydrates with protein or fat to slow digestion. The studies that showed the strongest results achieved a glycemic index difference of about 12 points between their old and new eating patterns. You don’t need to eliminate carbs entirely. You need to choose ones that break down slowly.
Fiber plays a direct role here. People with type 2 diabetes who ate the most fiber were about half as likely to have poor blood sugar control compared to those who ate the least. Fiber slows the rate at which glucose enters your bloodstream after a meal, blunting the spikes that drive sugar onto your red blood cells. Good sources include beans, lentils, vegetables, nuts, and whole grains. Aim for 25 to 30 grams per day, which most people don’t come close to.
Exercise Lowers A1C Regardless of Type
Both aerobic exercise (walking, cycling, swimming) and resistance training (weights, bands, bodyweight exercises) lower A1C. A systematic review and meta-analysis found that resistance training reduced A1C by 0.39 percentage points compared to inactive controls, and there was no statistically significant difference between resistance and aerobic training. In other words, the best exercise for your A1C is whichever type you’ll actually do consistently.
The American Diabetes Association recommends at least 150 minutes per week of moderate activity, ideally a combination of both aerobic and resistance training. That’s roughly 30 minutes, five days a week. Spacing matters too: try not to go more than two consecutive days without some form of exercise, because the insulin-sensitizing effects of a single session fade after about 48 hours.
Exercise works partly by helping your muscles absorb glucose without needing as much insulin, and partly by improving how sensitive your cells are to insulin over time. These effects are independent of weight loss, meaning even if the scale doesn’t move, your blood sugar control improves.
Sleep Has a Bigger Impact Than Most People Realize
Sleeping less than about six hours a night directly impairs your body’s ability to process sugar. An NIH-funded study found that six weeks of mild sleep restriction (6.2 hours or less per night) increased insulin resistance by nearly 15%. For postmenopausal women, the effect was even more pronounced, reaching about 20%. When your cells resist insulin, your body needs to produce more of it to keep blood sugar in check, and eventually it can’t keep up. The result is higher fasting glucose and, over time, a higher A1C.
If you’re doing everything else right but consistently getting five or six hours of sleep, that alone could be undermining your progress. Prioritizing seven to eight hours is one of the few changes that costs nothing and requires no willpower during the day.
How Medication Fits In
When lifestyle changes aren’t enough to reach your target A1C, medication can make a substantial difference. Metformin, the most commonly prescribed first-line drug, typically lowers A1C by about 1 to 1.5 percentage points. Newer injectable medications work by mimicking a gut hormone that stimulates insulin release and slows digestion. Among these, the reductions vary widely depending on the specific drug and dose: some lower A1C by roughly 0.5 to 1.0 points, while the most potent options have shown reductions of over 2 percentage points in clinical trials.
Your doctor will choose a medication based on your starting A1C, other health conditions, side effect profile, and cost. Many people start with a single medication and add or switch if they’re not reaching their goal after three months. Medication works best when layered on top of diet and exercise changes, not as a replacement for them.
Putting It All Together
Each individual intervention might lower your A1C by a fraction of a percentage point, but these effects compound. Switching to lower-glycemic meals, adding 150 minutes of weekly exercise, sleeping seven-plus hours, and managing stress can collectively bring your number down by a full point or more, sometimes enough to move from the diabetes range back into prediabetes, or from prediabetes back to normal.
The key is consistency over weeks and months, not perfection on any single day. One high-sugar meal doesn’t ruin your A1C. A pattern of high-sugar meals over 90 days does. Start with the change that feels most achievable, build the habit, then layer on the next one. Your A1C will follow.