From the Guidelines
Metformin can lower A1c by 1-2 percentage points, with most patients seeing reductions of about 1.5% on average, and the time to reach the lowest A1c is usually 2-3 months, as supported by the most recent guidelines 1. The medication works gradually to improve insulin sensitivity and reduce glucose production by the liver. The maximum effect generally occurs within 3 months of starting the medication or reaching the optimal dose. Your results will vary based on your starting A1c level, dosage (typically 500-2000mg daily), adherence to the medication, and whether you're making lifestyle changes alongside medication therapy. Some key points to consider when using metformin include:
- Most patients start with a low dose (500mg once daily) and gradually increase to minimize gastrointestinal side effects, with the full therapeutic dose often being 1000-2000mg daily divided into two doses.
- For best results, combine metformin with dietary changes, regular physical activity, and weight management if needed, as these factors significantly enhance the medication's effectiveness in lowering blood glucose levels.
- It is essential to monitor your A1c levels and adjust your treatment plan as needed to achieve and maintain your individualized glycemic goals, as recommended by the latest standards of care in diabetes 1.
- When A1C is ≥1.5% above the individualized glycemic goal, many individuals will require dual-combination therapy or a more potent glucose-lowering agent to achieve and maintain their goal A1C level 1.
From the FDA Drug Label
The results are presented in Table 7 Table 7: Mean Change in Fasting Plasma Glucose and HbA1c at Week 29 Comparing Metformin Hydrochloride Tablets vs Placebo in Patients with Type 2 Diabetes Mellitus *Not statistically significant Metformin Hydrochloride Tablets (n=141) Placebo (n=145) p-Value FPG (mg/dL) Baseline 241.5 237.7 NS * Change at FINAL VISIT –53.0 6.3 0.001 Hemoglobin A1c (%) Baseline 8.4 8.2 NS * Change at FINAL VISIT –1. 4 0.4 0.001
The maximum reduction in HbA1c on metformin is -1.7% as seen in Table 8. The time it takes to achieve this reduction is 29 weeks. Key points:
- The reduction in HbA1c is statistically significant.
- The study was conducted with metformin hydrochloride tablets up to 2550 mg/day.
- The baseline HbA1c was around 8.4% to 8.8%. 2
From the Research
A1c Levels on Metformin
- The study 3 found that 61% of participants achieved A1c <7% after 12 weeks of metformin treatment, with a mean change of -1.3% from 7.7% at the start.
- Another study 4 showed that metformin significantly reduced A1c levels compared to placebo, with a decrease of 0.007 in A1c levels after 12 weeks.
- The study 5 found that a 1-unit increase in time-weighted hemoglobin A1c levels was associated with modestly lower cognitive performance scores.
Time to Achieve Desired A1c Levels
- The study 3 found that after 12 weeks of metformin treatment, 61% of participants achieved A1c <7%, and after 26 weeks, 43% of participants with insulin detemir achieved A1c <7%.
- The study 4 showed that metformin reduced A1c levels after 12 weeks of treatment.
- The study 5 found that the choice of second-line glucose-lowering medication class added to metformin was not associated with change in cognitive performance in persons with early type 2 diabetes.
Factors Affecting A1c Levels
- The study 6 found that insulin therapy is recommended for patients with type 2 diabetes mellitus and an initial A1C level greater than 9 percent, or if diabetes is uncontrolled despite optimal oral glycemic therapy.
- The study 7 showed that metformin reduced HbA1c levels and insulin dosage in adolescents with type 1 diabetes mellitus.
- The study 5 found that worse glycemic control is associated with modestly worse cognitive performance.