If you have diabetes, your doctor might suggest Toujeo (insulin glargine) as a treatment option for you. Knowing Toujeo’s possible side effects can help you and your doctor decide whether to add it to your treatment plan.

Toujeo is a prescription medication that’s used to treat type 1 or type 2 diabetes in adults and some children. Toujeo is not used to treat diabetic ketoacidosis.

Toujeo is a long-acting insulin that’s available as a liquid solution. It comes in prefilled pens (Toujeo SoloStar or Toujeo Max SoloStar) that you use to inject the drug under your skin.

If Toujeo works to manage your blood sugar, your doctor may recommend that you use it long term to treat your diabetes.

For more information about Toujeo, see this in-depth article.

Like other drugs, Toujeo can cause mild or serious side effects. Keep reading to learn more.

Some people may experience mild or serious side effects during their Toujeo treatment. Examples of Toujeo’s commonly reported side effects include:

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

Keep reading to learn about other possible mild and serious side effects of Toujeo.

Most side effects that occur from Toujeo are mild. Examples of mild side effects that have been reported with Toujeo include:

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

In most cases, these side effects should be temporary. And some may be easily managed, too. But if you have any symptoms that are ongoing or that bother you, talk with your doctor or pharmacist. And don’t stop using Toujeo unless your doctor recommends it.

Toujeo may cause mild side effects other than the ones listed above. See the Toujeo prescribing information for details.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with Toujeo, visit MedWatch.

It’s possible to develop serious side effects from Toujeo. Serious side effects that have been reported with this drug include:

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

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

Get answers to some frequently asked questions about Toujeo’s side effects.

Does Toujeo cause diarrhea?

No, diarrhea isn’t a side effect of Toujeo. In studies, people receiving this medication didn’t report having diarrhea.

But other diabetes medications, such as Fortamet (metformin), may cause diarrhea.

If you have diarrhea while you’re receiving Toujeo, talk with your doctor about what may be causing it. They may be able to recommend ways to help stop this side effect from occurring.

Is joint pain a side effect of Toujeo?

No, joint pain isn’t a side effect of Toujeo. Joint pain wasn’t reported in studies of people receiving this drug.

But it’s possible for other medications that treat diabetes to cause joint pain. For example, Lantus (insulin glargine)* can cause joint pain.

If you have joint pain during Toujeo treatment, ask your doctor about what’s causing it. They should be able to recommend the best ways to treat this side effect.

* Toujeo and Lantus both have the same active ingredient, insulin glargine. But studies of Lantus reported different side effects from those reported in studies of Toujeo.

Does Toujeo cause sleepiness?

No, Toujeo shouldn’t cause you to feel sleepy. Studies of people receiving Toujeo didn’t report this side effect.

But it’s possible to feel sleepy due to diabetes itself. For example, high or low blood sugar can cause you to feel more tired than usual.

If you’re experiencing sleepiness during Toujeo treatment, talk with your doctor. They may recommend testing your blood sugar levels when you’re sleepy to see if they’re high or low. Your doctor may also recommend ways to decrease the sleepiness that you’re feeling.

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

Weight gain

You may have weight gain from receiving Toujeo. This medication, along with other insulin treatments, may cause weight gain to occur. This is a common side effect reported by people taking Toujeo in studies.

What might help

If you have unexpected weight gain, talk with your doctor. In some cases, weight gain may be due to other conditions, such as heart failure. Your doctor may evaluate you to be sure nothing else is causing the weight gain. They may also be able to recommend ways to maintain a moderate weight.

For tips on managing weight gain while taking insulin, such as Toujeo, see this article.

Injection site reactions

You may have injection site reactions from Toujeo. These are side effects that occur in an area where you injected the drug. In studies, injection site reactions were one of the most commonly reported side effects.

Examples of injection site reactions to watch out for include:

  • redness or discoloration
  • swelling
  • itching

What might help

If you experience a reaction at the site of a Toujeo injection, talk with your doctor. They’ll check to make sure that you’re not having an allergic reaction. Then they’ll be able to recommend ways to treat this side effect. For example, they may recommend taking an over-the-counter (OTC) medication, such as Benadryl (diphenhydramine), to ease your symptoms.

Low blood sugar

Toujeo can cause low blood sugar. This is a common side effect of the drug, and in some cases, it can be severe or even life threatening.

You should be aware of the symptoms of low blood sugar so that you can treat it right away. Symptoms to watch for include:

What might help

Before starting Toujeo treatment, your doctor will likely discuss with you how to prevent and treat low blood sugar. They may recommend that you monitor your blood sugar levels more often throughout your treatment.

If you develop symptoms of low blood sugar, eat 15 grams (g) of carbohydrates. Then after 15 minutes, test your blood sugar level to see if it’s increased to normal. If it’s still low, you should repeat this process.

Examples of food or drink that contain 15 grams of carbohydrates include:

  • 4 ounces of juice or regular soda
  • 1 tablespoon of sugar, honey, or corn syrup
  • hard candies or jelly beans

For more information about how to prevent or treat low blood sugar, talk with your doctor.

Allergic reaction

Like most drugs, Toujeo can cause an allergic reaction in some people.

Symptoms can be mild or serious and can include:

  • skin rash
  • itchiness
  • flushing (temporary warmth, redness, or deepening of skin color)
  • swelling under your skin, typically in your eyelids, lips, hands, or feet
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. To manage your symptoms, they may suggest an OTC antihistamine you take by mouth, such as Benadryl (diphenhydramine). Or they may recommend a product you apply to your skin, such as hydrocortisone cream.

If your doctor confirms you had a mild allergic reaction to Toujeo, they’ll decide if you should continue using it.

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 had a serious allergic reaction to Toujeo, they may have you switch to a different treatment.

Keeping track of side effects

During your Toujeo treatment, consider keeping notes on any side effects you’re having. Then, you can share this information with your doctor. This is especially helpful to do 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 receiving when you had the side effect
  • how soon after starting that dose you had the side effect
  • what your symptoms were from the side effect
  • how it affected your daily activities
  • what other medications you were also taking
  • any other information you feel is important

Keeping notes and sharing them with your doctor will help your doctor learn more about how Toujeo affects you. And your doctor can use this information to adjust your treatment plan if needed.

Toujeo may not be right for you if you have certain medical conditions or other factors that affect your health. Talk with your doctor about your health history before Toujeo treatment. The list below includes factors to consider.

Kidney problems. If you have kidney problems, Toujeo can increase your risk of low blood sugar. Before starting Toujeo treatment, tell your doctor about any kidney problems you may have. They’ll likely recommend that you monitor your blood sugar levels more often throughout treatment.

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

Liver problems. Before starting Toujeo treatment, discuss any liver problems that you have with your doctor. Liver problems may increase your risk of low blood sugar. If you have liver problems, your doctor may recommend that you monitor your blood sugar levels more often throughout treatment.

Heart problems. If you have heart failure, tell your doctor. Using Toujeo while taking another type of diabetes medication called thiazolidinediones (TZDs) may worsen this condition. Examples of TZDs include Actos (pioglitazone) and Avandia (rosiglitazone). Your doctor may recommend monitoring your heart failure more often. Or they may suggest taking a medication other than the TZD for your diabetes.

Alcohol use and Toujeo

Your doctor will likely recommend that you avoid drinking alcohol during Toujeo treatment. This is because alcohol may affect the way that Toujeo works to manage your blood sugar.

For more about how alcohol affects Toujeo, talk with your doctor.

Pregnancy and breastfeeding while receiving Toujeo

It’s not known if Toujeo is safe to use during pregnancy or breastfeeding.

If you’re pregnant or breastfeeding, or planning to become pregnant or breastfeed, talk with your doctor before starting Toujeo treatment. They can help you determine the right treatment for your diabetes during pregnancy or breastfeeding.

In most cases, side effects from Toujeo are mild. But you may develop severe side effects from the drug, though this is rare.

Before you start using Toujeo, you may want to discuss possible side effects with your doctor. Below are some questions to get you started:

  • Do my other medical conditions increase my risk of side effects from Toujeo?
  • If I develop side effects from Toujeo, what’s the best way to treat them?
  • What should I do if I become pregnant during Toujeo treatment?
  • How can I prevent side effects that Toujeo may cause from occurring?

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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.