The most commonly used medication for type 2 diabetes is metformin, which has historically been the first-line treatment. But today’s treatment landscape includes several drug classes, and your doctor may recommend one or more depending on your blood sugar levels, weight, heart health, and kidney function. When blood sugar is significantly above target at diagnosis, combination therapy with two medications from the start is common practice.
Metformin: The Traditional Starting Point
Metformin works in three ways: it reduces the amount of glucose your liver produces, decreases how much sugar your intestines absorb from food, and helps your cells respond better to insulin. It typically lowers A1c (a measure of average blood sugar over three months) by about 1 percentage point at doses up to 1,500 mg per day.
Most people start on 500 mg once or twice daily, with the dose gradually increasing to a maintenance level of 850 to 1,000 mg twice daily. An extended-release version allows for once-daily dosing, which can reduce the most common side effects: stomach upset, nausea, and diarrhea. Metformin does not cause weight gain, and it carries a very low risk of dangerous blood sugar drops, which makes it a practical long-term option for most people.
GLP-1 Receptor Agonists
GLP-1 receptor agonists (sometimes called GLP-1 drugs) mimic a natural gut hormone that triggers insulin release after you eat, slows digestion, and reduces appetite. Because they only boost insulin when blood sugar is elevated, the risk of low blood sugar is low. The most well-known drugs in this class are semaglutide and liraglutide, both given by injection.
These medications produce significant weight loss on top of blood sugar control. In trials of people with type 2 diabetes and obesity, semaglutide at the higher dose led to an average weight loss of about 9.7 kg (roughly 21 pounds) over the study period. Liraglutide at its highest dose produced average losses of around 7 to 9 kg. The most common side effects are nausea, diarrhea, and vomiting, which tend to improve over the first few weeks as the dose is gradually increased.
Tirzepatide: The Dual-Action Newcomer
Tirzepatide activates two gut hormone receptors instead of one, combining the effects of GLP-1 with a second hormone called GIP. This dual action produces a stronger insulin response and greater blood sugar reduction than single-target GLP-1 drugs alone.
In clinical trials, the highest dose of tirzepatide lowered A1c by 2.4 percentage points from a starting level of 8%, compared to 1.1 points for the GLP-1 drug dulaglutide. Weight loss was also substantially greater: participants on 15 mg of tirzepatide lost an average of 11.3 kg (about 25 pounds) over 26 weeks, while those on dulaglutide lost 2.7 kg. At the 10 mg dose, 39% of participants lost more than 10% of their body weight. Side effects are similar to GLP-1 drugs, primarily nausea and digestive discomfort.
SGLT2 Inhibitors
SGLT2 inhibitors, including empagliflozin, dapagliflozin, and canagliflozin, work through the kidneys. They block a protein that normally reabsorbs sugar back into your bloodstream, so excess glucose leaves your body through urine instead. They lower A1c by roughly 0.7 percentage points and carry a low risk of hypoglycemia.
What sets this class apart is its protective effects on the heart and kidneys. A large meta-analysis of three major trials found that SGLT2 inhibitors reduced the risk of heart failure hospitalization by 38% and slowed kidney disease progression by 45%. These benefits exist even in people whose blood sugar is already reasonably controlled, which is why doctors often choose SGLT2 inhibitors specifically for patients with existing heart or kidney disease.
Because these drugs increase sugar in the urine, urinary tract and genital yeast infections are more common. A rarer but serious concern is a form of ketoacidosis that occurs even when blood sugar readings look normal. This can be triggered by surgery, severe illness, dehydration, or prolonged fasting while taking the medication.
DPP-4 Inhibitors
DPP-4 inhibitors work on the same hormonal system as GLP-1 drugs, but less aggressively. After you eat, your gut releases hormones that signal your pancreas to produce insulin. An enzyme called DPP-4 normally breaks these hormones down within minutes. DPP-4 inhibitors block that enzyme, allowing the hormones to stay active longer and keep blood sugar in check.
These medications lower A1c by about 0.75 percentage points. They don’t cause weight gain or loss (they’re considered “weight neutral”), and they have a low risk of hypoglycemia. They’re taken as a daily pill, which some people prefer over the injections required for GLP-1 drugs. DPP-4 inhibitors are generally well tolerated, though they’re less potent than GLP-1 agonists or SGLT2 inhibitors for both blood sugar and any additional heart or kidney benefits.
Sulfonylureas and Meglitinides
Sulfonylureas (such as glipizide and glimepiride) and meglitinides (such as repaglinide) stimulate your pancreas to release more insulin regardless of whether your blood sugar is high or low. This direct stimulation makes them effective at lowering blood sugar, but it also creates the highest risk of hypoglycemia of any diabetes drug class. They also tend to cause weight gain.
Meglitinides work faster and wear off sooner than sulfonylureas, which gives them a somewhat lower hypoglycemia risk. They’re taken just before meals. Both drug classes are older and less expensive, which keeps them in use, particularly in settings where cost is a primary concern. However, newer drug classes with fewer side effects and added heart or kidney benefits have largely moved sulfonylureas out of the first-choice position in current treatment guidelines.
Insulin Therapy
Some people with type 2 diabetes eventually need insulin, especially if the pancreas can no longer produce enough on its own. Insulin therapy for type 2 diabetes usually starts with a single daily injection of long-acting (basal) insulin, which provides a steady background level to control blood sugar between meals and overnight.
If basal insulin alone isn’t enough, rapid-acting (bolus) insulin can be added before meals to handle the blood sugar spike from eating. Rapid-acting insulin starts working within 15 minutes, peaks within one to three hours, and wears off in about four to five hours. The general goal is a roughly 50/50 split between basal and mealtime insulin in the total daily dose. Timing matters: rapid-acting insulin is typically injected within 15 minutes of eating, while regular insulin needs to be taken 30 minutes before a meal.
One practical risk with mealtime insulin is “stacking,” which happens when you take a correction dose too soon after your previous injection. Because rapid-acting insulin stays active for four to six hours, injecting again within that window can cause blood sugar to drop dangerously low. Spacing doses at least four hours apart helps avoid this.
How Doctors Choose Between Them
The choice of medication depends on more than just blood sugar numbers. For someone with heart failure or chronic kidney disease, SGLT2 inhibitors offer benefits beyond glucose control. For someone whose primary concern is weight, a GLP-1 agonist or tirzepatide may be the better fit. Cost, insurance coverage, and whether a person prefers pills over injections all factor in.
When A1c is 1.5 to 2 percentage points above the target at diagnosis, current guidelines recommend starting with two medications right away rather than trying one and waiting. This approach gets blood sugar to goal faster, which reduces the risk of complications. Many people with type 2 diabetes will use more than one medication class over the course of their treatment, either in combination or sequentially as the disease progresses.