Medication for type 2 diabetes

Photo of a woman measuring her blood sugar (PantherMedia / Miriam Doerr)

People with type 2 diabetes have an increased risk of various medical conditions, including heart attacks and strokes. Depending on their age and lifestyle, different people may have different treatment goals and use different medications. These will also depend on whether they have any other health problems.

Since high blood sugar levels (hyperglycemia) are the main sign of type 2 diabetes, it seems logical to use blood-sugar-lowering medication. But that isn’t always necessary. Medication is only needed if blood sugar levels can’t be regulated any other way, for example by changing your diet, losing weight or exercising more.

Constantly high blood sugar levels can cause damage to blood vessels and nerves. This can lead to medical problems affecting the kidneys, feet and retina (the lining of the back of the eye). The risk of stroke or heart attack may also increase. But this depends on things like the age at which type 2 diabetes starts. In many older people with type 2 diabetes, the increased blood sugar levels don’t cause any problems. Other conditions like high blood pressure are often more of a problem for them.

If you’re diagnosed with type 2 diabetes at about the age of 40, you will probably live with the condition for quite a long time. But if younger people develop type 2 diabetes, even slightly too high blood sugar levels can lead to other problems over a long period of time. It is therefore very important for them to keep their blood sugar levels down.

Drugs for lowering the risk of cardiovascular disease

Type 2 diabetes increases the risk of cardiovascular (heart and blood vessel) disease. People with diabetes often have other risk factors as well, like high blood pressure. It is then quite likely that treating those other factors with medication may lower the risk of a heart attack or stroke more effectively than keeping blood sugar levels down. The main types of medication are:

All of these medications can have side effects. It is important to consult your doctor before taking any of them. This is also true if the medications are available without a prescription, like Aspirin.

People who have one or more of the complications of type 2 diabetes, such as retina damage, might need medications for those problems too.

Tablets for lowering blood sugar (antidiabetics)

Most people with type 2 diabetes don’t have to inject insulin. If they can’t lower their blood sugar by changing their lifestyle, they can take tablets known as antidiabetics. If one type of medication isn’t enough, it can be combined with other blood-sugar-lowering tablets.

Research has shown that keeping blood sugar levels down reduces the risk of damage to small blood vessels, particularly in the eye. But it isn’t clear how well antidiabetics help to prevent complications such as heart attacks and strokes. There are hardly any long-term studies in this area. There also isn’t enough research on how the different medications compare.

All antidiabetics can cause blood sugar levels to drop too low sometimes. Too-low blood sugar is known as hypoglycemia.

The most established medications for treating type 2 diabetes are:

  • Metformin: This drug reduces the amount of glucose produced by the body, and has been used for a long time. It's the best studied diabetes medication, as well as one of the best tolerated. For this reason, doctors usually recommend trying metformin first. The possible side effects include diarrhea and feeling unwell, especially if metformin isn’t taken together with a meal.
  • Sulfonylureas: These drugs help the body to produce more insulin. Like metformin, these drugs have also been in use for quite a while. Hypoglycemia is a bit more common when using sulfonylureas than when using metformin. Some people also gain weight when they start the treatment. Others may have allergic reactions to sulfonylureas.

Newer antidiabetic drugs include:

  • Glitazones: These drugs help the cells to use insulin more effectively. The drug rosiglitazone was taken off the market in 2010 because it probably increases the risk of a heart attack. Only pioglitazone is still approved for the treatment of diabetes in Germany. Compared to sulfonylureas, pioglitazone is less likely to cause hypoglycemia. Possible side effects include weight gain, bone fractures, water retention and heart failure. The European Medicines Agency (EMA) warns that pioglitazone may slightly increase the risk of bladder cancer. Due to the possible side effects, pioglitazone is not the medication of first choice, and is only prescribed to a small number of patients.
  • Glinides: Glinides include the drugs nateglinide and repaglinide. They increase insulin production in the body. Compared to metformin, glinides are more likely to lead to mild and moderate hypoglycemia. Glinides can cause weight gain.
  • Gliptins (dipeptidyl peptidase-4 inhibitors): Gliptins also stimulate the production of insulin. They include the drugs linagliptin, saxagliptin, vildagliptin and sitagliptin.
  • Gliflozins (SGLT-2 inhibitors): Gliflozins include the drugs dapagliflozin, empagliflozin and canagliflozin. They cause more sugar to be excreted in urine, lowering blood sugar levels.

Drugs known as alpha-glucosidase inhibitors were used in the treatment of type 2 diabetes in the past, but they are rarely used for this purpose nowadays. They slow down the intake of glucose in the bowel. The most commonly used drug in this group is called acarbose. It causes a lot of side effects, particularly flatulence and diarrhea. Compared to other options, it doesn’t lower blood sugar levels as much.

In very rare cases (about 1 out of 10,000 per year), people with type 2 diabetes who take metformin develop acidosis. This is the medical term for too much acid in the blood, which can lead to breathing problems, nausea or circulatory shock. It can be caused by a number of different things, but metformin is thought to be a contributing factor. Because of this, people with decreased kidney function, decreased heart function or an alcohol dependence aren’t allowed to take these antidiabetics at all, or only if they take certain precautions.

Research summaries

Insulin

All people with type 1 diabetes have to inject insulin. People with type 2 diabetes usually only need insulin if they can’t control their blood sugar enough by taking tablets. Two different types of insulin are available: human insulin and insulin analogues. Both are genetically engineered, but have different chemical structures. Short-acting insulin analogues can lower blood sugar a bit faster than human insulin can. But there is no proof that this has any added health benefits. Human insulin and insulin analogues work equally well in the treatment of type 2 diabetes.

Several studies have looked into whether it makes sense to use insulin or a combination of different antidiabetic drugs if blood sugar can’t be lowered enough by using a single antidiabetic drug and/or making changes to diet and exercise habits. This is what was found:

  • There was no difference between insulin and combinations of antidiabetics in terms of the long-term consequences of diabetes, such as heart problems.
  • Insulin was better at lowering blood sugar.
  • In people who took antidiabetic drugs, hypoglycemia was less common, but other side effects – particularly affecting the stomach and bowel – were more common.

Incretin mimetics

Incretin mimetics are hormone-like drugs that can be injected in addition to taking metformin and/or sulfonylurea tablets. They are not supposed to replace antidiabetic tablets. They can be used instead of, or in addition to, insulin. The drug is injected under the skin with a pre-filled pen. Incretin mimetics stimulate the pancreas to make more insulin. It’s not yet clear whether treatment with incretin mimetics has any long-term advantages. Examples of incretin mimetics include the drugs liraglutide, dulaglutide, lixisenatide, exenatide and albiglutide. The possible side effects include nausea and vomiting.

Which medication is most suitable?

Blood-sugar-lowering drugs work in some people and don’t work in others. Whether or not a person needs to take antidiabetic medication at all, which drugs are most suitable, and how much their blood sugar levels should be lowered depends on a number of different factors:

The risk of severe hypoglycemia is also important when choosing the right medication. To avoid this side effect, it may be a good idea to aim for blood sugar levels that are a little too high. This particularly applies to older people.