Farxiga (dapagliflozin) typically lowers A1C by 0.4% to 0.8% and reduces fasting blood sugar by about 24 to 29 mg/dL, depending on the dose and whether it’s used alone or with other medications. These numbers come from 24-week clinical trials, and your individual results will depend on where your blood sugar starts, your kidney function, and what else you’re taking.
A1C Reduction by Dose
In clinical trials of the 5 mg dose, patients saw an average A1C drop of about 0.37%. The 10 mg dose performed slightly better, lowering A1C by roughly 0.42%. These results were measured at 24 weeks, with patients also taking insulin alongside Farxiga.
When used as the sole diabetes medication in people with type 2 diabetes, the A1C reductions tend to be larger, often in the range of 0.6% to 0.8%. That’s because patients who aren’t already on other glucose-lowering drugs have more room for improvement. If your A1C is 8.5%, for example, Farxiga alone might bring it closer to 7.7% or 8.0% over six months. Combined with metformin or insulin, the total effect is additive, meaning both drugs contribute to a greater overall reduction than either would achieve on its own.
Fasting Blood Sugar Changes
Fasting blood sugar, the number you see first thing in the morning or before meals, drops meaningfully with Farxiga. In a study of people with untreated type 2 diabetes, the 5 mg dose lowered fasting glucose by 24.1 mg/dL after 24 weeks. The 10 mg dose brought it down by 28.8 mg/dL. For comparison, patients on a placebo saw only a 4.1 mg/dL decrease over the same period.
So if your fasting blood sugar is sitting around 170 mg/dL, Farxiga at the higher dose could bring it down to roughly 140 mg/dL on its own. That’s a meaningful shift, though it’s rarely enough by itself to reach the typical target of under 130 mg/dL for most people with type 2 diabetes. It’s more commonly paired with metformin or other medications to close the remaining gap.
How Farxiga Lowers Glucose
Farxiga works through a completely different pathway than most diabetes drugs. Instead of increasing insulin or making your cells more sensitive to it, Farxiga blocks a protein in your kidneys that normally reabsorbs sugar back into your bloodstream. With that protein blocked, excess glucose passes out through your urine instead of cycling back into your blood. You essentially urinate out the extra sugar.
This mechanism has a few practical implications. First, it works regardless of how well your pancreas produces insulin, which is why it’s effective across a wide range of diabetes severity. Second, the glucose-lowering effect is self-limiting. As your blood sugar drops closer to normal, there’s less excess sugar for the kidneys to filter out, which means Farxiga carries a low risk of pushing blood sugar dangerously low on its own. Third, because you’re excreting calories as sugar in your urine, weight loss is a common side effect. Clinical studies showed patients lost about 6 pounds over 24 weeks on either dose, and 6 to 7 pounds when combining Farxiga with metformin.
After-Meal Blood Sugar Spikes
Farxiga also blunts the blood sugar spikes that happen after eating. Because the kidneys are continuously filtering out glucose throughout the day, the peak blood sugar level after a meal doesn’t climb as high as it otherwise would. This is a meaningful benefit since post-meal spikes contribute significantly to overall A1C and are linked to cardiovascular risk. The effect isn’t as dramatic as what you’d see with a rapid-acting insulin, but it provides steady, around-the-clock glucose removal that smooths out the highs.
Kidney Function Matters
Because Farxiga works through the kidneys, its blood sugar lowering ability depends heavily on how well your kidneys are functioning. The drug becomes less effective at reducing glucose as kidney function declines, since the kidneys filter less blood (and therefore less sugar) per minute. Farxiga is generally not prescribed for blood sugar control in people with severely reduced kidney function, typically those with an eGFR below 25 or so. It’s worth noting that Farxiga is sometimes still prescribed at lower kidney function levels for heart or kidney protection, but the glucose-lowering benefit at that point is minimal.
If your doctor has mentioned that your kidney function is borderline, the A1C and fasting glucose reductions you experience may be smaller than the clinical trial averages listed above. Those trials enrolled patients with relatively preserved kidney function.
How Quickly It Works
Farxiga begins lowering blood sugar within the first day of taking it. Since it works by physically blocking sugar reabsorption in the kidneys, the effect kicks in as soon as the drug reaches therapeutic levels in your body. You may notice lower fasting numbers within the first week. However, the full A1C impact takes about 12 to 24 weeks to show up in lab work, since A1C reflects your average blood sugar over the previous two to three months. Your doctor will likely recheck your A1C after three to six months to see how well the medication is working.
What Affects Your Individual Results
The numbers from clinical trials are averages, and several factors influence where you’ll land within the range. A higher starting A1C generally means a bigger absolute drop, simply because there’s more glucose circulating for the kidneys to clear. People starting with an A1C of 9% or higher often see reductions of 1% or more, while those starting around 7.5% may see a smaller numerical change.
Diet and exercise interact with Farxiga’s effects as well. If you’re eating large amounts of carbohydrates, your kidneys can only clear so much sugar per day, and the overflow stays in your blood. Farxiga removes roughly 50 to 80 grams of glucose per day through urine, which equals about 200 to 300 calories. That’s a meaningful amount, but not unlimited. Patients who combine the medication with moderate carbohydrate control tend to see the best results.
Other medications matter too. If you’re adding Farxiga to metformin, a sulfonylurea, or insulin, the combined A1C reduction will be greater than Farxiga alone. The flip side is that combining it with insulin or sulfonylureas increases the chance of low blood sugar episodes, something Farxiga rarely causes on its own.