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If you have type 2 diabetes, you’ve probably heard of metformin. It’s the medication doctors typically prescribe first when you’re diagnosed.

Metformin is a tablet that lowers blood sugar levels by keeping your liver from releasing too much sugar, also called glucose, into your blood. It also makes your body more sensitive to insulin -- the hormone that controls your blood sugar. Metformin makes the cells in your muscles, fat, and liver react to insulin more efficiently so they can better absorb glucose from your blood.

There are a few reasons why metformin is the typical first choice for diabetes treatment. It’s unlikely to make your blood sugar dip too low the way other medicines can. And it doesn’t cause weight gain. Some people even lose a little bit of weight when they take metformin.

Doctors prescribe this medicine when a healthy diet and exercise routine aren’t doing enough to keep blood sugar levels under control. It may be the only medication you take for diabetes, or you may need others, too. But it’s likely not a good option if you have:

  • Liver or kidney problems
  • A bad infection
  • Heart failure or had a recent heart attack
  • An allergy to the medication

Metformin has some common side effects, including: 

  • Nausea
  • Diarrhea
  • Vomiting
  • Stomachache
  • Loss of appetite
  • Metallic taste in your mouth

You can ease these problems if you take the medicine with food or if your doctor starts you at a low dose of the medicine and gradually raises it. For many people, side effects go away after a few weeks as your body gets used to the medicine.

Some people will have more serious side effects, like a vitamin B12 deficiency. If you take metformin along with another diabetes medicines, your blood sugar levels could drop too low, a condition called hypoglycemia. Metformin can also cause a serious condition called lactic acidosis, when too much lactic acid builds up in your body. But this is very rare, and it usually affects people who have another serious health problem, like kidney failure, liver disease, or heart failure. But if you notice any of the signs -- stomach pain, low appetite, diarrhea, fast breathing, muscle cramps, weakness, or tiredness -- call your doctor right away.


GLP-1 stands for glucagon-like peptide 1. It’s a hormone that helps control your pancreas, the organ that releases insulin into your bloodstream.

GLP-1 receptor agonists work by acting like those hormones. They tell your pancreas to release more insulin after you eat. They also slow down the rate that food leaves your stomach after you digest it, helping you feel full longer after a meal. All of these things help lower the amount of glucose in your blood.

GLP-1 receptor agonists come in pills or as a liquid you inject into your thigh, upper arm, or stomach. You might take them by themselves or with other diabetes medications. Because of the way they affect your appetite and digestion, you may be hungry less often when you take them. You may also lose weight.

Other common side effects include:

  • Nausea
  • Vomiting
  • Dizziness
  • Weakness
  • Headache
  • Diarrhea

Your doctor may recommend these medicines if you’re at risk for heart disease because they seem to lower the chance of heart failure and heart attacks. But they can raise your risk of pancreatitis (an inflamed pancreas), so tell your doctor if you have any pain in your belly along with nausea and vomiting. By themselves, they don’t tend to make your blood sugar go too low (a condition called hypoglycemia), but this could be an issue if you also take other diabetes meds or insulin.


SGLT2 stands for sodium glucose co-transporter 2, a part of kidney cells that help them take in glucose. SGLT2 inhibitors block those parts and keep your kidneys from absorbing glucose from your urine back into your blood. Instead, the extra glucose goes out of your body in your urine.

You take these drugs as a pill, usually once a day. Most of the time, doctors prescribe them when you’ve already been taking at least one diabetes medicine but it hasn’t lowered your blood sugar enough.

These medicines can be a solution for people at high risk for heart disease. They lower your chances of heart attack, heart failure, and stroke. They also can cause weight loss.

They aren’t a good option, though, if you have kidney disease or need dialysis. And there are some risks to taking these medicines. You may need to pee more often, and they raise your chances of getting urinary tract infections and yeast infections. You also have a higher chance of a serious complication called diabetic ketoacidosis. One type of SGLT2 inhibitor, canagliflozin (Invokana), is linked to a higher risk of lower limb amputation in some people. Your doctor will watch your health closely for signs of these problems.

Diabetes medicine and your heart

Diabetes and your heart


These tablets target the part of your pancreas that makes insulin, called beta cells. They tell these cells to make more insulin than usual. You take the medication with a meal, either once or twice a day.

You might take these drugs if you’re having trouble keeping your blood sugar levels low enough with another medication. Doctors often prescribe them along with metformin. But they can eventually stop working, and you’ll need to switch to a different type of medicine.

It’s possible for your blood sugar levels to go too low when you take sulfonylureas, so you should watch for signs of hypoglycemia, including:

  • Shakiness or dizziness
  • Sweating
  • Hunger
  • Irritability
  • Anxiety
  • Headache

Doctors often recommend carrying a quick source of carbs with you in case your blood sugar gets too low. If you find this happens often, you may need to adjust your dose.

Other side effects of sulfonylureas include:

  • Increased hunger
  • Weight gain
  • Skin rash
  • Upset stomach


Like sulfonylureas, these medications tell your pancreas to make more insulin. But they work more quickly and wear off faster than sulfonylureas. You typically take them three times a day, right before a meal.

Your doctor might prescribe these medications for you because your blood sugar levels are moderately high. A common side effect is hypoglycemia -- low blood sugar. You're more likely to have this side effect if you take other diabetes medications along with meglitinides. Your risk of hypoglycemia is slightly lower with these drugs than it is with sulfonylureas.

You may also have:

  • Headaches
  • Nausea
  • Stomach pain

You shouldn’t drink alcohol while taking this medicine. The mixture of the two can make you feel sick, get flushed, or vomit.


DPP-4 is a chemical your body makes. It breaks down the hormone GLP-1, which tells your pancreas to release insulin after you eat.

Usually, DPP-4 works within minutes to destroy GLP-1 and stop the pancreas from releasing insulin. But when you take a DPP-4 inhibitor, it blocks your DPP-4 enzymes. That lets GLP-1 last longer in your body, keeping insulin flowing and lowering blood sugar.

These medicines don’t lower blood sugar levels as dramatically as others do. Your doctor will likely suggest you try a DPP-4 inhibitor after you’ve tried other diabetes drugs first. You take them as tablets, either along with other medications or by themselves.

You probably won't gain weight on DPP-4 inhibitors. And they don’t cause blood sugar to dip too low the way other medicines can. But they raise your odds of getting pancreatitis.

Side effects are typically mild and include:

  • Joint pain
  • Nausea
  • Diarrhea
  • Stomach cramps
  • Sore throat
  • Stuffy nose
  • Upper respiratory infection
  • A higher risk of going to the hospital for heart failure


These medicines help prevent the spike in blood sugar that happens right after you eat. They’re sometimes called “starch blockers” because they delay the breakdown of carbohydrates like bread, pasta, and potatoes as well as sugar. They block key enzymes so that you digest carbohydrates slower, and they lower the amount of glucose your small intestine absorbs from food.

You take them only with the first bite of a meal. Usually, this means you take them three times a day. You don’t take them if you skip a meal.

They come with a few side effects like:

  • Gas
  • Bloating
  • Cramps
  • Diarrhea

Doctors typically try other medications to lower your blood sugar before they prescribe alpha-glucosidase inhibitors. If they’re the only medicine you take for your diabetes, they’re not likely to make your blood sugar levels dip too low. You’re also not likely to gain or lose weight because of them.


These once-daily tablets work in the same way as metformin. They make your body react better and more quickly to insulin. They help your fat, liver, and muscles take in more glucose. Your liver also puts out less glucose into your bloodstream when you take them. That leads to lower blood sugar levels.

Though they do the same thing in your body, doctors don’t prescribe thiazolidinediones as often as metformin. They’re linked to weight gain and raise your risk of serious conditions, such as:

  • Anemia
  • Heart failure
  • Heart attacks
  • Bladder cancer
  • Broken bones in people with osteoporosis


Insulin is a hormone your body makes. It tells your body when to store glucose and when to let more into your bloodstream. If your blood sugar levels are regularly high, you may need to give yourself shots of insulin.

It’s unlikely your doctor would choose insulin first as a treatment for your type 2 diabetes. The timing of doses can be tricky. But it can be a key player when blood sugar is hard to control.

Different types of insulin work in different ways to lower blood sugar, so your doctor will talk with you about which is best for you. Some insulin shots last for 24 hours. Others you take right before you eat to lower the glucose spike that happens after a meal. You may need a mixture of different types. Often, if you’re taking diabetes medications that help your body use insulin better, your doctor will prescribe extra insulin to go along with your medication. This is called combination therapy.

You might notice changes on your skin where you give yourself the shot, including redness or itching. Insulin can also make you gain weight.

If you take too much insulin, or exercise too much, or don’t eat enough -- or even get too stressed -- you can get hypoglycemia. Insulin may not work well in your body if you have:

  • Congestive heart failure
  • Low potassium
  • Infection
  • Kidney disease
  • Liver disease

Using insulin to keep a tighter control on your blood sugar levels can boost your energy and also help lower your risk of:

  • Eye damage
  • Nerve damage
  • Kidney disease


Though medications are important tools for blood sugar control, diet, exercise, restful sleep, and weight loss play a huge role in your diabetes management. Doctors often begin treatment of type 2 diabetes by recommending changes to what you eat, a focus on exercise, and safe ways to lose weight and increase fitness.

For some people, these changes are enough to get the condition under control without taking diabetes medication. If you do need medicine, these healthy habits are still an important part of your treatment.

You can start with simple changes like:

  • Picking up a new exercise habit, like a daily walk
  • Cutting back on sugary foods and drinks (candy, soda, juice)
  • Watching portion sizes
  • Eating meals that focus on vegetables, whole grains, lean protein, and healthy fats

Exercise can help your body use extra glucose. Getting to a healthy weight can help your body use less insulin. If you’re carrying extra pounds, losing even a few can help you turn glucose into energy. Over time, you may also find you need less medication to manage your diabetes. That means fewer side effects and a greater sense of well-being. 

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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for general informational purposes only and does not address individual circumstances. It is not a substitute for professional medical advice, diagnosis or treatment and should not be relied on to make decisions about your health. Never ignore professional medical advice in seeking treatment because of something you have read on the WebMD Site. If you think you may have a medical emergency, immediately call your doctor or dial 911.

Reviewed by Brunilda Nazario, MD on October 7, 2019


Mayo Clinic: “Type 2 Diabetes,” “Insulin Human Regular (Injection Route),” “Intensive insulin therapy: Tight blood sugar control.”

NHS: “Metformin.”

Hormone Health Society: “GLP1 Receptor Agonists.”

Johns Hopkins Patient Guide to Diabetes: “SGLT2 Inhibitors,” “DPP-IV Inhibitors,” “Alpha glucosidase inhibitors.”

Joslin Diabetes Center: “Oral Diabetes Medications Summary Chart.”

Agency for Healthcare Research and Quality: “Oral Diabetes Medications Fact Sheet.”

Cleveland Clinic: “Oral Diabetes Medications,” “Do You Worry About Getting Insulin Shots for Type 2 Diabetes?”

NYU Langone Health: “Medication for Type 2 Diabetes in Adults.”

American Diabetes Association: “What are my options?” “Oral medication.”