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What is Januvia used for and how does it work?

Medically reviewed by Leigh Ann Anderson, PharmD. Last updated on May 8, 2023.

Official answer


Key Points

  • Januvia (generic name: sitagliptin) is a prescription oral diabetes tablet taken once daily, along with diet and exercise, to help to lower blood sugar levels (glucose) in adults living with type 2 diabetes.
  • Januvia works by adjusting the levels of insulin and glucose your body makes after eating. It is taken once a day and is used in addition to diet and exercise to improve your blood sugar control (measured by an A1C test).
  • Januvia is not for treating type 1 diabetes or diabetic ketoacidosis (increased ketones in your blood or urine).

How Januvia works

Januvia (sitagliptin), from Merck, works by targeting two key problems in type 2 diabetes: it increases insulin production in the pancreas and decreases glucose overproduction in the liver. When used in addition to diet and exercise, Januvia has been shown to improve blood sugar control (your A1C).

Januvia is thought to work by slowing the inactivation of incretin hormones (GLP-1 and GIP) released by your intestine throughout the day and in response to a meal. Incretin hormones are part of a complex system that helps to regulate your blood sugar.

Normally, incretin hormones are rapidly deactivated by an enzyme called dipeptidyl peptidase 4 (DPP-4). However, Januvia is in a class of drugs known as dipeptidyl peptidase 4 (DPP-4) inhibitors, which work by blocking the deactivation of incretin hormones. By increasing and prolonging active incretin levels, Januvia increases insulin release from the pancreas and decreases glucagon levels and glucose release from the liver. Januvia works in response to your differing blood sugar levels.

Other FDA approved medications in the DPP-4 inhibitor class include saxagliptin (Onglyza), linagliptin (Tradjenta), and alogliptin (Nesina). These medicines come as single-ingredient products or combined with other diabetes medicines such as metformin.

  • DPP-4 inhibitors improve blood glucose control and reduce your blood glucose levels both after and in between meals without causing weight gain.
  • Another advantage to DPP-4 inhibitors is that they do not usually cause low blood sugar levels (hypoglycemia) unless they are combined with other medicines that also cause low blood sugar.

How can Januvia help me with my diabetes?

Many patients first diagnosed with type 2 diabetes start on an oral medication known as metformin. It’s in the class of drugs known as biguanides. It increases your cells ability to utilize glucose (blood sugar) by improving how your insulin works and decreases liver glucose production and absorption.

However, some patients cannot reach their goal with metformin alone and need extra medication.

Januvia can be added to metformin to help you reach your A1C goal. Sitigliptin, the active ingredient in Januvia, is also available in combination with metformin (Janumet and Janumet XR) in a fixed-dose tablet for ease of administration.

What is A1C?

A1C is a simple blood test that shows the average amount of sugar (glucose) in your blood over the past 2 to 3 months, letting you know how well your blood sugar is being controlled over time. It is often used to diagnose as well as monitor type 2 diabetes. A1C is also called HbA1c or the glycated hemoglobin A1C test.

Your A1C test will report numbers that let you know your risk for diabetes and consider lifestyle changes like exercise or diet. It can help your doctor know if you need to adjust any medication doses.

  • Normal A1C levels are below 5.7%
  • Levels between 5.7% and 6.4% percent are considered prediabetes.
  • Levels of 6.5% or higher on two separate tests means you have diabetes.

Different medical groups recommend different A1C levels, so it’s always best to ask your doctor what’s best for you. The American Diabetes Association recommends an A1C goal of less than 7% for most adults. In 2018, the American College of Physicians (ACP) released guidance suggesting that an A1C target goal should be between 7% and 8%.

What works for one patient may not be the best target goal for everyone. Some people might need a higher or lower A1C goal based on their age, medications they take, or other factors. You’ll typically have this test twice a year if you’re meeting your treatment goals.

How do I take Januvia?

  • Take Januvia one time each day exactly as your doctor tells you. It comes in a 25 mg, 50 mg or 100 mg tablet you swallow. You can take Januvia with or without food.
  • The recommended dose of Januvia is 100 mg once daily, but you may need a different dose. If you have a certain level of kidney disease or are on dialysis, your doctor may need to adjust your dose.
  • Do not take Januvia if you are allergic to any of its ingredients.

Januvia is not approved for use by anyone younger than 18 years of age.

If you miss a dose, take it as soon as you remember. If it’s time for your next dose, skip the medication and get back on your normal schedule. Don’t take 2 tablets at the same time.

Check your blood sugar as your doctor recommends and stick to your diet and exercise program every day.

Low blood sugar may occur more frequently if you take Januvia with certain other medications, such as insulin or sulfonylureas.

  • Talk to your doctor about how to prevent, recognize and manage high blood sugar, low blood sugar and any diabetes complications you might have.
  • If you take other medications for type 2 diabetes, your doctor may need to lower your Januvia dose.

Signs and symptoms of low blood sugar may include:

  • headache
  • drowsiness
  • irritability
  • hunger
  • dizziness
  • confusion
  • sweating
  • feeling jittery
  • weakness
  • fast heartbeat

To quickly treat hypoglycemia, eat or drink a fast-acting source of sugar such as fruit juice, crackers, or a non-diet soda that contains sugar.

What are the side effects with Januvia?

All drugs have side effects and come with some level of risk. However, the risk from untreated type 2 diabetes can also adversely impact your health. Left untreated, type 2 diabetes can cause serious medical problems such as nerve and kidney damage, vision problems, and heart disease.

In general, Januvia is well-tolerated. In studies, the overall incidence of side effects, low blood sugar, and discontinuation of Januvia due to side effects were similar to placebo (an inactive pill).

Before you start Januvia, tell your doctor if you have a history of pancreatitis, heart failure or heart disease, or kidney disease. Also, tell your doctor if you are pregnant or planning on having a baby.

If you have any concerns about the following side effects, speak with your doctor.

Serious side effects with Januvia may include:

  • low blood sugar, especially when used with other medications for diabetes such as insulin or sulfonylureas (for example, glipizide, glyburide or glimepiride)
  • pancreatitis (inflammation of the pancreas)
  • serious allergic reactions
  • heart failure
  • kidney problems that may lead to dialysis.
  • severe joint pain (arthralgia)
  • serious skin reaction called a bullous pemphigoid with DPP-4 inhibitors. Call your doctor immediately if you develop blisters or the breakdown of the outer layer of your skin (erosion). You may need to stop taking Januvia.

Common side effects with Januvia (occuring in >5%, or 5 out of 100 patients):

  • upper respiratory infection
  • stuffy or runny nose and sore throat
  • headache.

Other side effects, including stomach upset, stomach pain and diarrhea have been reported. Swelling of the hands or legs, when Januvia is used with rosiglitazone (Avandia), another type of diabetes medication, may occur.

Bottom Line

Januvia (sitagliptin) is an oral types 2 diabetes medicine that can help you lower your blood sugar and reach your target goals. It is used along with diet and exercise. It typically does not cause low blood sugar or weight gain when used alone without other diabetes medications.

It’s in a class of drugs known as dipeptidyl peptidase 4 (DPP-4) inhibitors. These drugs work in the pancreas and the liver to help you increase insulin and lower your blood sugar levels.

Merck’s Januvia is often used with metformin and comes in combination tablets for this purpose called Janumet (sitagliptin and metformin) and Janumet XR, an extended-released form of Janumet, also from Merck.

Januvia is usually well-tolerated. However, as with all drugs , there are side effects and you should discuss with your doctor.

This is not all the information you need to know about Januvia for safe and effective use. Review the full Januvia information here, and speak to your health care provider if you have questions or concerns.


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