Toujeo (insulin glargine) is a prescription brand-name medication. It’s approved by the Food and Drug Administration (FDA) to treat type 1 or type 2 diabetes. The drug is for use in adults as well as children ages 6 years and older.

Toujeo is meant to be used as a long-term treatment for managing blood sugar levels.

Here are some fast facts about Toujeo:

Like other drugs, Toujeo can cause side effects. Read on to learn about potential common, mild, and serious side effects. For a general overview of Toujeo, see this article.

Toujeo can cause certain side effects, some of which are more common than others. These side effects may be temporary, lasting a few days to weeks. However, if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

These are just a few of the more common side effects reported by people who took Toujeo in clinical trials:

* For more information about this side effect, see “Side effect specifics” below.

Mild side effects can occur with Toujeo use. This list doesn’t include all possible mild side effects of the drug. For more information, you can refer to Toujeo’s prescribing information.

Mild side effects that have been reported with Toujeo include:

These side effects may be temporary, lasting a few days to weeks. However, if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks side effects of the medication. If you develop a side effect during Toujeo treatment and want to tell the FDA about it, visit MedWatch.

* For more information about this side effect, see “Side effect specifics” below.

Toujeo may cause serious side effects. The list below may not include all possible serious side effects of the drug. For more information, you can refer to Toujeo’s prescribing information.

If you develop serious side effects while using Toujeo, 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.

Serious side effects that have been reported and their symptoms include:

* This side effect did not occur during clinical studies of Toujeo. However, it’s a known side effect of insulin. (Toujeo is a type of insulin.)
† For more information about this side effect, see “Side effect specifics” below.

Learn more about some of the side effects that Toujeo may cause.

Site reactions from SoloStar pens

The use of Toujeo can cause injection site reactions. Site reactions are common side effects of insulin pens. It’s not clear how often these side effects occurred in clinical trials of Toujeo pens.

The following reactions can happen around the area of skin where Toujeo is injected:

  • itching
  • rash
  • redness or discoloration
  • swelling
  • lipodystrophy (skin dimpling)

What you can do

Be sure to avoid injecting Toujeo in an area of skin that’s damaged, bruised, tender, hard, or scaly. Toujeo may not work as well if it’s injected into these areas.

It’s important to rotate injection sites each time you inject Toujeo. This helps lower your risk of site reactions. You can inject Toujeo under the skin of your abdomen, upper arm, or thigh.

If you’re concerned about having site reactions while using Toujeo SoloStar pens, talk with your doctor. They can suggest other ways to help relieve this side effect.

Weight gain

Weight gain is possible with Toujeo. This is a common side effect of all insulin medications, including Toujeo. However, it isn’t clear how often weight gain occurred in clinical trials of the drug.

Weight gain from insulin happens because of how the drug works in your body. Insulin helps your cells remove sugar from the blood. Some of this sugar may be stored as body fat, which can lead to weight gain over time.

What you can do

If you’re concerned about weight gain while using Toujeo, talk with your doctor. They can suggest ways to help you maintain a moderate weight. This may involve eating a nutritious diet and exercising, for example.

Upper respiratory infection

Upper respiratory infections (URIs) are possible with Toujeo. In clinical trials, the common cold was the most common type of URI reported. Other specific infections that occurred in clinical trials of Toujeo aren’t known.

Symptoms of URIs can include:

What you can do

Tell your doctor if you have any symptoms of a URI while using Toujeo. They can suggest ways to ease your symptoms. These may include resting, drinking lots of fluids, and trying an over-the-counter cold remedy. Be sure to check with your doctor first before trying to treat a URI on your own.

Allergic reaction

As with most drugs, Toujeo can cause an allergic reaction in some people. In clinical trials, mild allergic reactions occurred around the area where Toujeo was injected.* However, it’s not clear whether serious allergic reactions occurred in clinical trials.

Symptoms can be mild or serious and can include:

  • skin rash
  • itching
  • flushing
  • swelling under your skin, typically in your lips, eyelids, feet, or hands
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

* For more information about this side effect, see “Site reactions from SoloStar pens” in the “Side effect specifics” section above.

What you can do

For mild symptoms of an allergic reaction, call your doctor right away. They may recommend ways to ease your symptoms and determine whether you should keep using Toujeo. However, if your symptoms are serious and you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Toujeo may cause several side effects. Here are some frequently asked questions about the drug’s side effects and their answers.

Is joint pain a side effect of Toujeo?

Toujeo isn’t likely to cause joint pain. This side effect wasn’t reported in clinical trials of the drug.

However, joint pain was reported as a side effect in clinical trials of a medication called Lantus.* Both Toujeo and Lantus contain insulin glargine as the active ingredient. So it’s possible that Toujeo may cause side effects similar to those of Lantus, including joint pain.

If you’re concerned about joint pain with Toujeo, talk with your doctor.

* To learn more about how Toujeo compares with Lantus, see this article.

Is diarrhea a side effect of Toujeo?

No, Toujeo isn’t known to cause diarrhea. This side effect wasn’t reported in clinical trials of the drug.

Diabetes, which Toujeo is used to treat, can lead to complications that cause diarrhea. For example, diabetes can cause nerve damage in the digestive system, which may lead to diarrhea.

Other diabetes drugs are also known to cause diarrhea. Examples include metformin (Fortamet, Glumetza, Riomet) and semaglutide (Ozempic). If you take these medications in combination with Toujeo, you may experience diarrhea. However, it’s likely a side effect of these other drugs instead of Toujeo itself.

If you have diarrhea while using Toujeo, talk with your doctor. They can determine if it’s caused by your condition, other medications you take, or something else. Your doctor can also suggest ways to relieve this side effect.

Does Toujeo cause sleepiness?

It’s not likely. Sleepiness wasn’t a side effect reported in clinical trials of Toujeo.

Toujeo is used to treat diabetes, and this condition may cause fatigue. Sleepiness can be a symptom of fatigue. Other symptoms of fatigue include muscle aches, irritability, and trouble concentrating.

If you feel sleepy or have other symptoms of fatigue while using Toujeo, talk with your doctor. The drug may not be working well to treat your diabetes. Your doctor can order tests to check how well your diabetes is being managed. They can also ask you about other possible causes of your sleepiness and recommend ways to feel more rested.

Be sure to talk with your doctor about your health history before Toujeo treatment. This drug may not be the right treatment for you if you have certain medical conditions or other factors that affect your health. The conditions and factors to consider include:

Hypokalemia. Toujeo can cause new or worseninghypokalemia (low level of potassium in the blood). This can lead to serious heart problems, including an irregular heart rate or rhythm.

Before starting Toujeo treatment, tell your doctor if you have hypokalemia. You should also tell them about all other health conditions you have and any medications you take. Your doctor can determine if these factors raise your risk of hypokalemia from Toujeo. Your doctor will likely monitor your potassium levels closely while you use the medication.

Heart failure. The use of Toujeo in combination with diabetes medications called thiazolidinediones (TZDs) can worsen heart failure. Examples of these drugs include Avandia (rosiglitazone) and Actos (pioglitazone). Before starting Toujeo treatment, tell your doctor if you have heart failure. You should also mention any other diabetes medications you take.

While using Toujeo, be sure to tell your doctor if you have any symptoms of worsening heart failure. This includes swelling of your ankles or feet and shortness of breath. Your doctor may have you stop taking TZD during your Toujeo treatment.

Liver or kidney problems. If you have liver or kidney problems, you may have an increased risk of low blood sugar with Toujeo. Examples of these problems include liver failure and kidney failure. Before starting treatment with Toujeo, tell your doctor about any liver or kidney problems you have. They can recommend ways to help prevent low blood sugar while you use this medication.

Allergic reaction. If you’ve had an allergic reaction to Toujeo or any of its ingredients, your doctor will likely not prescribe Toujeo. Ask them what other medications may be better options for you.

Alcohol and Toujeo

It’s best to avoid alcohol during your Toujeo treatment. This is because drinking alcohol can change your blood sugar levels. The changes in these levels can affect how well Toujeo works to manage your condition.

Keep in mind that some liquid medications, such as liquid NyQuil, contain small amounts of alcohol as an inactive ingredient. If possible, it’s best to limit the use of medications that contain alcohol while you use Toujeo.

Before starting treatment with Toujeo, tell your doctor about all medications you take. They can determine if those drugs contain alcohol.

If you drink alcohol, talk with your doctor about how much alcohol (if any) is safe to consume during Toujeo treatment.

Pregnancy and breastfeeding while using Toujeo

It isn’t known for sure whether Toujeo is safe to use while pregnant or breastfeeding. The drug hasn’t been specifically studied during pregnancy or breastfeeding. The drug also hasn’t been studied in children who were breastfed by someone who used Toujeo.

In general, the American Diabetes Association considers insulin (such as Toujeo) to be safe and effective for use while pregnant or breastfeeding.

If you’re pregnant or planning to become pregnant, talk with your doctor. You should also talk with them if you’re breastfeeding or considering it. They can discuss the risks and benefits of Toujeo treatment during these times.

Mild and serious side effects can occur with Toujeo. Most side effects are mild and should go away with time. However, be sure to tell your doctor if you have bothersome side effects from Toujeo.

If you’d like to learn more about Toujeo, talk with your doctor or pharmacist. They can help answer any questions you have about its side effects.

Besides talking with your doctor, you can do some research on your own. These articles might help:

  • More information about Toujeo. For details about other aspects of Toujeo, refer to this article.
  • Dosage details. You can find out about Toujeo’s dosage with this article.
  • Drug comparison. To learn how Toujeo compares with Lantus, read this article.
  • A look at diabetes. For more information about diabetes, see our diabetes hub and list of diabetes articles.

Disclaimer: Medical News Today 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.