Janumet (sitagliptin/metformin) is a prescription drug that’s prescribed to help manage type 2 diabetes. Janumet can cause side effects that range from mild to serious. Examples include pancreatitis and diarrhea.

Specifically, Janumet and Janumet XR are used to manage blood sugar levels in adults with type 2 diabetes. For this use, both drugs are prescribed along with diet and exercise plans.

Keep reading to learn about the common, mild, and serious side effects that Janumet can cause. For a general overview of the drug, including details about its uses and the differences between the forms, see this article.

Janumet has a boxed warning. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). For details, see the “Side effects explained” section below.

Some people may experience mild to serious side effects during treatment with Janumet or Janumet XR. Examples of commonly reported side effects of these drugs include:

* To learn more about this side effect, see the “Side effects explained” section below.

These are just a few of the side effects these drugs may cause. And not everyone who takes these drugs will have side effects. Continue reading for more information on mild to serious side effects of Janumet and Janumet XR.

Some people who take Janumet or Janumet XR will have mild side effects. Examples that have been reported with these drugs include:

* To learn more about this side effect, see the “Side effects explained” section below.

In most cases, these side effects should be temporary. Some may be easily managed, too. But if you have symptoms that are ongoing or bother you, talk with your doctor or pharmacist. And do not stop taking Janumet or Janumet XR unless your doctor recommends it.

These drugs may cause mild side effects other than those listed above. For details, see the prescribing information for Janumet and Janumet XR.

People with liver, kidney, or heart problems are more likely to have serious side effects from Janumet and Janumet XR. Serious side effects that have been reported with these drugs include:

If you develop serious side effects while taking Janumet or Janumet XR, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

* To learn more about this side effect, see the “Side effects explained” section below.
† Janumet and Janumet XR have a boxed warning for this side effect. This is the most serious warning from the FDA. To learn more, see the “Side effects explained” section below.

Allergic reaction

For some people, Janumet can cause an allergic reaction.

But it’s not clear whether this side effect occurred in studies of Janumet and Janumet XR.

In general, symptoms of allergic reaction can be mild or serious. You can learn more about possible symptoms in this article.

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest a treatment to manage your symptoms and can determine whether you should keep taking Janumet.

If you have symptoms of a severe allergic reaction, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.

If your doctor confirms you’ve had a serious allergic reaction to Janumet, they may have you switch to a different treatment.

Get answers to some frequently asked questions about Janumet and Janumet XR’s side effects.

Is there an increased risk of side effects with the 50 mg/1,000 mg doses of Janumet and Janumet XR compared with lower strengths of these drugs?

Yes — the lower dose is less likely to cause side effects. This is why your doctor will increase your dose slowly over time. The 50-milligram (mg)/1,000-mg dose refers to 50 mg of sitagliptin and 1,000 mg of metformin.

Starting treatment with a low dose can help reduce certain side effects of metformin. These include abdominal pain, nausea, vomiting, and diarrhea.

If you’ve never taken metformin, your starting dosage of Janumet would likely be 50 mg sitagliptin/500 mg metformin taken twice daily. For Janumet XR, the initial dosage is typically 50 mg sitagliptin/500 mg extended-release metformin taken once daily. Then, your doctor may slowly increase your dosage over time. This approach helps your body adjust to the medication.

If you have a kidney problem, higher strengths of this drug may not be safe for you to take. This is because kidney problems may increase the risk of side effects, such as lactic acidosis. If you have a kidney problem, talk with your doctor before starting treatment. They’ll determine the safest dosage for you.

Can Janumet and Janumet XR cause pancreatic cancer?

No, it’s not expected to. Pancreatic cancer wasn’t a reported side effect in studies of Janumet or Janumet XR. But people who took the drugs in these studies did report pancreatitis. This is a serious side effect that may be life threatening.

If you have questions about how Janumet or Janumet XR may affect your pancreatic health, talk with your doctor.

Do Janumet and Janumet XR cause hair loss or blurry vision?

No, it shouldn’t. Blurry vision and hair loss were not seen as side effects in studies of Janumet and Janumet XR.

However, blurry vision can be a symptom of hypoglycemia (low blood sugar). Janumet and Janumet XR can cause low blood sugar in people who also take certain other diabetes medications. Examples include insulin, such as insulin lispro (Humalog), and sulfonylureas, such as glimepiride (Amaryl).

If you notice blurry vision, talk with your doctor about managing your blood sugar level. And be sure to have regular eye exams to monitor for other causes of vision changes. If you notice hair loss, your doctor can help determine the cause and recommend ways to manage it.

How long do Janumet and Janumet XR side effects last?

It depends on the side effect. Diarrhea, nausea, and other digestion-related side effects are very common when you first start taking Janumet or Janumet XR. (This is the case with any medication that contains metformin). Taking your dose with a meal can help lessen these side effects. And they should go away within a few days to weeks as you continue treatment.

Janumet XR may be a better option than Janumet for people who continue to have digestion-related side effects. This is because Janumet XR contains an extended-release form of metformin, which is often easier to tolerate. (“Extended-release” means the drug releases slowly into your body over a longer period.)

Other side effects of Janumet or Janumet XR may go away more quickly with treatment. For example, a headache can be treated with a pain reliever, such as ibuprofen (Advil) or Tylenol (acetaminophen).

If you have side effects from Janumet or Janumet XR that don’t go away or become severe, talk with your doctor.

Is weight loss a possible side effect of Janumet and Janumet XR?

Yes, weight loss is possible when you take Janumet or Janumet XR.

But these medications aren’t approved for this use. If you lose weight while taking these drugs, you may gain the weight back if you stop taking them.

A healthy way to lose weight is to exercise and eat a nutritious diet. Janumet and Janumet XR are meant to be used along with diet and exercise to treat type 2 diabetes.

Learn more about some of the side effects Janumet and Janumet XR may cause.

Risk of lactic acidosis

Janumet and Janumet XR have a boxed warning for the risk of lactic acidosis. This is a rare but serious side effect of these drugs. It was not reported in studies of Janumet or Janumet XR. But it was reported in studies of metformin (an active ingredient in these drugs). A boxed warning is a serious warning from the FDA. Due to this risk, doctors will use caution when prescribing these drugs for people with certain conditions.

With lactic acidosis, too much lactic acid builds up in your blood and tissues. This condition can cause other complications, such as atypical heart rhythms. Without treatment, lactic acidosis could become fatal.

Certain factors can increase your risk of lactic acidosis. If you already have a problem with your kidneys, liver, or heart, your risk may be higher. Drinking alcohol is also a risk factor. You can talk with your doctor about ways to decrease your risk of this serious side effect.

Some symptoms of lactic acidosis include:

What might help

If you notice symptoms of lactic acidosis, contact a healthcare professional right away. If you think your life might be in danger, call 911 or your local emergency number.

Lactic acidosis is a medical emergency. It will need to be treated at a medical facility. If you have this side effect, you’ll stop taking Janumet or Janumet XR.

If you have risk factors for lactic acidosis, you can take steps to help manage those risks. For example, if you have a kidney problem, take your medication and keep up with blood tests and doctor visits. If you drink alcohol, your doctor may recommend limiting the amount you consume. Talk with your doctor about avoiding medications that may interact with metformin.

Hypoglycemia

Hypoglycemia (low blood sugar) is a rare side effect of Janumet and Janumet XR. In studies, this side effect occurred in people who took Janumet or Janumet XR with certain other diabetes drugs. Examples include insulin and sulfonylurea medications.

It’s important to treat low blood sugar before it becomes severe. The symptoms of mild low blood sugar can be easy to miss and include:

Symptoms of very low blood sugar are more severe and can include:

What might help

You can check your blood sugar at home several times per day. There are many kinds of blood sugar monitors, some of which can be connected to a smartphone. So you can choose one that works best for your day-to-day life.

If you notice that your blood sugar is low, consume 15 grams of sugar. This can be in the form of a glucose tablet or 4 ounces of juice or non-diet soda. Wait 15 minutes, then measure your blood sugar again. If it’s still low, repeat this process. If it’s back to usual, you can have a snack or a meal. Talk with your doctor about your strategy for safely increasing your blood sugar.

If you have very low blood sugar, you may need to be treated at a medical facility. You or someone with you should call 911 or your local emergency number.

Headache

Headache was a common side effect in studies of Janumet and Janumet XR.

Headaches can be mild to severe. Symptoms may include dull, throbbing head pain. Headache symptoms can make it hard to concentrate or go about your normal routine.

What might help

You can treat a mild headache with over-the-counter pain medication, such as ibuprofen or acetaminophen. Lifestyle changes may also help prevent headaches. It’s important to drink enough water, get a good night’s sleep, exercise, and avoid consuming too much caffeine or alcohol. And if certain foods trigger your headaches, it may help to avoid them.

If you have bothersome or severe headaches while taking this medication, tell your doctor. They can suggest ways to manage your symptoms.

Bullous pemphigoid

Bullous pemphigoid is a rare immune system reaction that causes blisters on your skin. This is due to your immune system mistakenly attacking your healthy skin.

This reaction wasn’t reported in studies of Janumet or Janumet XR. But it was found in some people who took drugs in the same class as sitagliptin, such as saxagliptin (Onglyza) and linagliptin (Tradjenta).

Sitagliptin is one of the active ingredients in Janumet. (An active ingredient is what makes a drug work.)

Symptoms of bullous pemphigoid include blisters on the skin of your arms, legs, or lower abdomen.

What might help

If you develop skin blisters while taking Janumet or Janumet XR, call your doctor right away. If they confirm you have bullous pemphigoid, they’ll have you stop taking the drug. They may prescribe treatments to ease your skin symptoms. They may also prescribe a different treatment option for managing your blood sugar.

Keeping track of side effects

During your Janumet or Janumet XR treatment, consider taking notes on any side effects you’re having. You can then share this information with your doctor. This is especially helpful when you first start taking new drugs or using a combination of treatments.

Your side effect notes can include things such as:

  • what dose of drug you were taking when you had the side effect
  • how soon you had the side effect after starting that dose
  • what your symptoms were
  • how it affected your daily activities
  • what other medications you were taking
  • any other information you feel is important

Keeping notes and sharing them with your doctor will help them learn more about how Janumet or Janumet XR affects you. They can then use this information to adjust your treatment plan if needed.

Below are warnings to keep in mind before taking Janumet or Janumet XR.

Boxed warning: Risk of lactic acidosis

Janumet and Janumet XR have a boxed warning for the risk of lactic acidosis. A boxed warning is the most serious warning from the FDA.

Lactic acidosis is when too much lactic acid builds up in your body. Without treatment, this condition could become fatal.

To learn more, see the “Side effects explained” section above.

Other warnings

Janumet and Janumet XR can sometimes cause harmful effects in people who have certain conditions. This is known as a drug-condition interaction. Other factors may also affect whether Janumet is a good treatment option for you.

Talk with your doctor about your health history before you take Janumet or Janumet XR. Be sure to tell them if any of the following factors apply to you:

  • low vitamin B12
  • heart failure
  • liver problems
  • planned surgery
  • upcoming imaging tests, such as an X-ray or CT scan
  • kidney damage
  • age 65 years or older
  • hypoglycemia (low blood sugar)
  • previous allergic reaction to Janumet or any of its ingredients
  • pregnancy
  • breastfeeding
  • alcohol consumption

Like most medications, Janumet and Janumet XR may cause mild or serious side effects. Most people who take Janumet or Janumet XR commonly have some mild side effects, especially right after starting treatment. Serious side effects are possible but aren’t common.

Be sure to ask your doctor any questions you have about Janumet or Janumet XR. Here are a few ideas to help get you started:

  • Will my side effects be the same if I take Janumet instead of Janumet XR?
  • How can I reduce my risk of lactic acidosis?
  • Do I need blood tests to monitor my kidney function during my treatment?
  • How long does it usually take for digestive side effects, like abdominal pain, to go away?
  • Will a lower dose decrease my side effects?

Q:

I’m currently taking propranolol. Why does that make it hard to tell when I’m having side effects of hypoglycemia (low blood sugar)?

Anonymous

A:

You can see when your blood sugar is low by measuring it with a glucometer, but your body will also show signs. These symptoms, which include a rapid heartbeat and sweating, let you know that you need to eat or drink something with sugar right away.

But propranolol makes your heart beat slower and stops you from sweating as much. So this drug hides two of your body’s signals that your blood sugar is too low. Other drugs in the same group as propranolol also hide these signs of low blood sugar. This group of drugs, called beta-blockers, are sometimes used to treat heart failure or high blood pressure.

This is not a reason to stop taking propranolol. Just be sure to check your blood sugar on a schedule. And talk with your doctor about ways to keep your blood sugar at a safe level throughout the day.

The Healthline Pharmacist TeamAnswers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.