The most common medicine for type 2 diabetes is metformin, which remains the first drug most people start. But diabetes treatment has expanded significantly, and the best medication for you depends on whether you have type 1 or type 2 diabetes, your heart and kidney health, your weight goals, and how well your blood sugar responds over time. Here’s what each major class of medication does and where it fits.
Metformin: The Starting Point for Type 2
Metformin works three ways: it reduces the amount of sugar your liver releases into your blood, limits how much sugar your gut absorbs from food, and helps your cells respond better to insulin. It’s inexpensive, widely available as a generic, and has decades of safety data behind it. Most people start on 500 mg once or twice daily, with the dose gradually increased as needed.
The main downside is stomach trouble. Up to 30% of people taking metformin experience diarrhea, nausea, or vomiting, especially early on. An extended-release version causes fewer gut symptoms for most people. Taking it with food also helps. For the majority of patients, these side effects ease within a few weeks.
GLP-1 Receptor Agonists
This injectable class has become one of the most important additions to diabetes care. GLP-1 receptor agonists (semaglutide, liraglutide, dulaglutide, and exenatide are the main ones still on the market) work by mimicking a gut hormone that kicks in after you eat. They prompt your pancreas to release more insulin when blood sugar is high, slow down how fast your stomach empties, and reduce appetite by acting on hunger signals in the brain. Because they only boost insulin when blood sugar is elevated, the risk of dangerously low blood sugar is low.
Weight loss is a significant bonus. On average, people lose about 3 kg (roughly 6.5 pounds) more than those on placebo, though newer formulations of semaglutide often produce substantially greater losses. The 2025 American Diabetes Association guidelines now recommend GLP-1 receptor agonists regardless of blood sugar levels for people with type 2 diabetes who also have cardiovascular disease or are at high risk for it.
Tirzepatide: The Dual-Action Newcomer
Tirzepatide activates two hormone receptors at once, targeting both GLP-1 and another gut hormone called GIP. GIP amplifies the effects of GLP-1, which is why tirzepatide has been called a “super GLP-1 agonist.” The combined action promotes stronger blood sugar control and more weight loss than older single-target drugs. Importantly, both hormones stimulate insulin only when blood sugar is actually elevated, which keeps the risk of hypoglycemia low.
SGLT2 Inhibitors
SGLT2 inhibitors (empagliflozin, dapagliflozin, canagliflozin) take a completely different approach. They block a protein in your kidneys that normally reabsorbs sugar back into your bloodstream, so you excrete excess glucose in your urine instead. The result is lower blood sugar, modest weight loss, and lower blood pressure.
What sets this class apart is its effect on the heart and kidneys. A large meta-analysis of over 90,000 patients found that SGLT2 inhibitors reduced heart failure hospitalizations by 30% and cardiovascular death by 14% overall. In one major trial, empagliflozin alone cut heart failure hospitalizations by 35%. These drugs also slow the progression of chronic kidney disease, even in people without diabetes. The ADA now recommends SGLT2 inhibitors for anyone with type 2 diabetes and heart failure, regardless of their blood sugar numbers.
DPP-4 Inhibitors
DPP-4 inhibitors (sitagliptin, saxagliptin, alogliptin, linagliptin) are oral pills that work on the same hormone system as GLP-1 drugs but in a milder way. Instead of mimicking GLP-1 directly, they block the enzyme that breaks it down, letting your body’s own GLP-1 stick around longer. They stimulate insulin in a meal-dependent way, so the risk of low blood sugar is markedly lower than with older drugs like sulfonylureas. The tradeoff is that their blood sugar lowering and weight effects are more modest. They’re a reasonable option for people who need something gentle added to metformin and prefer a pill over an injection.
Sulfonylureas
Sulfonylureas (glipizide, glyburide, glimepiride) are among the oldest diabetes drugs still in use. They push your pancreas to release more insulin regardless of whether blood sugar is high, which makes them effective but carries a real risk of hypoglycemia, especially if you skip meals or exercise more than usual. They also tend to cause weight gain. Their biggest advantage is cost: they’re available as cheap generics. They’ve been largely displaced by newer classes for most patients, but they remain an option when affordability is the primary concern.
Thiazolidinediones
Pioglitazone is the main drug left in this class. It improves how your cells respond to insulin, particularly in fat and muscle tissue. It’s effective at lowering blood sugar, but it comes with notable drawbacks: fluid retention, weight gain (driven by increased fat storage and appetite), and a higher risk of bone fractures. People with moderate to severe heart failure should avoid it entirely because the fluid retention can worsen their condition. It’s also contraindicated in active bladder cancer and during pregnancy. For these reasons, pioglitazone is typically reserved for situations where other options haven’t worked or aren’t tolerated.
Insulin for Type 1 and Advanced Type 2
Everyone with type 1 diabetes needs insulin, because their immune system has destroyed the cells that produce it. Many people with long-standing type 2 diabetes eventually need insulin as well, when their pancreas can no longer keep up even with other medications on board.
Insulin comes in several speeds. Rapid-acting versions (like insulin lispro and aspart) start working within 15 minutes and cover the blood sugar spike from a meal. Long-acting versions (like insulin glargine) have no pronounced peak and provide a steady background level for 24 hours or more. Ultra-long-acting insulin degludec lasts up to 42 hours, offering more flexibility in timing. Most people on insulin use a combination: a long-acting injection once daily for baseline coverage, plus rapid-acting doses before meals.
Insulin pumps offer an alternative to multiple daily injections. A pump delivers rapid-acting insulin continuously through a small catheter under the skin, with programmable rates that can be adjusted throughout the day. Newer closed-loop systems pair a pump with a continuous glucose monitor to automate much of the dosing. Pumps are most common in type 1 diabetes, especially in children, where the flexibility in meal timing and the ability to fine-tune doses make a practical difference.
How Doctors Choose Between These Options
For most people newly diagnosed with type 2 diabetes, metformin is still the first prescription. What comes next depends heavily on your other health conditions. The 2025 ADA guidelines are clear on this: if you have cardiovascular disease or high cardiovascular risk, a GLP-1 receptor agonist or SGLT2 inhibitor should be part of your regimen whether or not your blood sugar is at target. If you have heart failure specifically, an SGLT2 inhibitor is the priority. If you have chronic kidney disease, both classes are recommended, though GLP-1 receptor agonists are preferred when kidney function is severely reduced.
Cost matters too. Metformin, sulfonylureas, and pioglitazone are all available as inexpensive generics. GLP-1 receptor agonists, SGLT2 inhibitors, and tirzepatide are brand-name drugs and significantly more expensive, though manufacturer programs and insurance coverage can reduce the out-of-pocket burden. For insulin specifically, Walmart sells Novo Nordisk human insulin (ReliOn) for about $25 per vial, and authorized generic versions of newer insulins are available at roughly half the brand-name list price.
Diabetes treatment is rarely one pill forever. Most people with type 2 diabetes add medications over time as the disease progresses, and the goal is always to match the right combination to your body’s needs, your risk factors, and your daily life.