If you’re looking for treatment options to manage your diabetes, your doctor might suggest NovoLog. It’s a prescription drug used to manage blood sugar levels in adults and children with diabetes mellitus. It’s a fast-acting insulin for type 1 or type 2 diabetes that you’ll likely use long term.

NovoLog comes as a liquid solution that you’ll inject under your skin. There are several forms of the drug:

  • The disposable pen is called the FlexPen.
  • The pen is used with a reuse pen.
  • The vonolog is used with a pump.

You may receive NovoLog by intravenous (IV) infusion (an injection into your vein given over time) if your condition is being treated in a hospital.

The active ingredient in NovoLog is insulin aspart. (An active ingredient is what makes a drug work.) It’s a certain kind of biologic, which is a drug made in a laboratory from living cells.

For more information about NovoLog, including details about its uses, see this in-depth article.

Outcome of drugs like NovoLog can be mild to serious. Continue reading to learn more.

The prefilled pen that was replaced by the NovoLog FlexPen is no longer available.

“Some people may experience side effects during their treatment. They don’t happen to everyone, but examples of side effects are reported.”

The side effects explained section is where you can learn more about this side effect.

The sections below contain more information about some of NovoLog’s mild and serious side effects.

Some people have side effects. Some examples have been reported.

The side effects explained section is where you can learn more about this side effect.

These side effects should be temporary. Some may be easy to manage. If you have any symptoms that bother you, talk to your doctor or pharmacist. Unless your doctor recommends it, you should not stop using it.

NovoLog may cause mild side effects other than the ones listed above. See the drug’s prescribing information for details.

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

Some people can experience serious side effects from using ovolog. Mild side effects are more common than serious ones. There have been serious side effects with this drug.

If you develop serious side effects while taking the drug, call your doctor. If they seem life threatening or you think you have a medical emergency, call the emergency number.

The side effects explained section is where you can learn more about this side effect.

There are many questions about the side effects of NovoLog.

Are NovoLog’s side effects similar to the side effects of Fiasp?

Yes, the side effects of NovoLog are similar to those of Fiasp. This is because they contain the same active ingredient, insulin aspart. (An active ingredient is what makes a drug work.) These side effects include:

Unlike NovoLog, Fiasp also contains niacinamide (vitamin B3) and L-arginine (an amino acid) to make it more stable and work faster. The side effects of these two drugs are similar, but some may occur at different rates since Fiasp works faster. For example, low blood sugar can occur more quickly with Fiasp.

You can learn more about the side effects of Fiasp by talking to your doctor.

Could using too much NovoLog cause side effects?

Side effects can be caused by taking too much of the drug. Depending on how your body responds to the overdose, these may be mild to severe. The side effects explained section explains some of the side effects of NovoLog.

A NovoLog overdose can cause serious side effects that can be life threatening, such as:

Call your doctor right away if you think you’ve taken too much NovoLog. You can also call 800-222-1222 to reach the American Association of Poison Control Centers or use its online resource. But if you have severe symptoms, immediately call 911 (or your local emergency number) or go to the nearest emergency room.

To learn more about a NovoLog overdose, see this in-depth article.

To help prevent overdose, be sure to take your dose of NovoLog exactly as your doctor prescribes. Using a medication reminder such as an alarm or phone app can help you remember when to take it. It can also help prevent accidental overdose from giving yourself extra injections or injections too close together.

Can I have side effects from using NovoLog in an insulin pump?

It’s possible. Side effects from Novolog are the same whether it’s given by an insulin pen, syringe, or insulin pump. But you may have side effects if the pump malfunctions and gives you the wrong dose. (See “Side effects explained” above to learn more about some of NovoLog’s side effects.) Incorrect NovoLog doses can cause serious side effects, such as:

If you use an injection pump, your doctor will show you how to inject yourself with the injection if the pump malfunctioned.

Follow the instructions from your doctor and the pump manufacturer. The manufacturer of the drug recommends against mixing the drug with other drugs. This will help prevent side effects.

“If it gets too hot or is left in the pump for too long, it can spoil. Since the drug isn’t working in your body as it should, you can have adverse effects such as high blood sugar. It is recommended that you change the NovoLog at least every 7 days. It may need to be sooner than 7 days.”

  • “The pump’s manufacturer has a recommendation.”
  • “The pump’s NovoLog has been exposed to a high temperature.”

Talk to your doctor about how to use your pump. They can answer any questions that you have about using a pump.

Learn about the side effects of NovoLog.

Weight gain

Some people may gain weight while using NovoLog. How often this side effect occurred in studies isn’t known. All insulin drugs may cause weight gain as a side effect because of how it works in your body. NovoLog removes sugar from your blood, which your cells use for energy. But some sugar is stored as fat, which your cells will use for energy later. Over time you may gain weight, especially if you have frequent swings in your blood sugar level.

If you gain or lose weight during your treatment, your dose of NovoLog may need to be adjusted.

Sudden weight gain can be dangerous. Your body might be retaining fluids, which can be a symptom of heart failure. Other diabetes drugs called thiazolidinediones can cause or worsen heart failure when taken together with NovoLog. Examples of thiazolidinediones include:

What might help

Regularly monitoring your blood sugar level while using NovoLog can help reduce large swings in your blood sugar that can cause weight gain.

To manage your weight, also try to exercise regularly and eat smaller meals throughout the day. Talk with your doctor about the right amount of daily calories your body needs. They can make recommendations on how to manage your weight while using NovoLog.


Changes in the thickness of your skin near an injection site is called lipodystrophy. The skin appears thick or dimpled due to repeated injections into the same spot. Injecting into these spots can cause the drug to not work properly and lead to hyperglycemia (high blood sugar). And suddenly changing injection sites to an unaffected area of skin can lead to hypoglycemia (low blood sugar).

What might help

You should rotate your injection sites when using NovoLog. If you use an injection pump, make sure to keep the sites clean.

If you notice that your skin looks rough, please tell your doctor. Before starting NovoLog, you should talk with your doctor about where to inject the drug and how to rotation it.


Hypoglycemia (low blood sugar) is the most common side effect caused by NovoLog. The drug works to lower blood sugar, but sometimes it can cause your blood sugar to get too low. This is usually a mild side effect. Symptoms include:

In rare cases, low blood sugar can occur. This is a medical emergency and can be life threatening. Severe low blood sugar can cause some symptoms.

If you have low blood sugar, you are at increased risk.

  • When your blood sugar is low, take NovoLog.
  • Are you fast?
  • take other diabetes drugs along with NovoLog
  • have liver or kidney problems

Talk to your doctor about mild to severe low blood sugar.

What might help

Regularly monitoring your blood sugar level while using NovoLog can help prevent low blood sugar. Your doctor may recommend that you measure your blood sugar with a portable device called a glucometer. They’ll recommend how often you need to do this based on the type of diabetes you have and your treatment plan.

If you notice that your blood sugar is low, you should consume at least 15 grams of Carbohydrates. Fast-acting carbohydrates include:

  • Hard candy is about 3 to 4 pieces.
  • A cup of juice or non- diet soda is 4 ounces.
  • The tablets contain sugar.
  • 1 part honey to 1 part water.

Check your blood sugar again after 15 minutes. Repeat this process until your blood sugar increases to a safe level. If you have symptoms of severe hypoglycemia, you or someone around you should call 911 for emergency help.

Hypokalemia (low potassium level)

NovoLog can cause hypokalemia (low potassium level), which can be life threatening. How often this side effect occurred wasn’t reported in the drug’s studies, but your risk may be higher if you have liver or kidney problems.

When combined with NovoLog, drinking large amounts of alcohol can lower your potassium levels. If you drink alcohol, talk to your doctor.

If you use a drug like NovoLog that lowers your level of potassium, you can increase your risk of low potassium. These include:

You may have symptoms if you have low potassium.

If you have concerns about low potassium levels, talk to your doctor.

What might help

Before starting NovoLog, you should talk to your doctor about your other medications. If you notice any symptoms of low potassium, call your doctor. If your level is too low, you will need to be hospitalized.

Allergic reaction

Some people can have an allergic reaction to NovoLog. Mild to serious symptoms can be present.

  • There is a skin rash.
  • It is itchy.
  • flushing (temporary warmth, redness, or deepening of skin color)
  • “It’s usually under your skin, but it can be anywhere.”
  • It can be hard to breathe if you have swelling of your mouth, tongue, or throat.

What might help

If you have a mild rash, call your doctor. They may suggest a treatment to help you. Examples include:

  • an antihistamine you take by mouth, such as Benadryl (diphenhydramine)
  • You apply a product to your skin.

If your doctor confirms that you have an allergic reaction to NovoLog, they will decide if you should continue using it.

If you have a severe allergic reaction, you should call the emergency number. These symptoms could be life threatening and need immediate medical care.

If your doctor confirms you have had a serious allergic reaction to NovoLog, they may want you to switch to another treatment.

Keeping track of side effects

Take notes on any side effects you are having during your treatment. You can share this information with your doctor. This is helpful when you are using a combination of treatments.

Side effect notes can include things.

  • When you had the side effect, what dose of the drug was taking?
  • How soon did you experience the side effect?
  • What are your symptoms?
  • How did it affect your daily activities?
  • What other drugs were you taking?
  • Other information is important to you.

Sharing notes with your doctor will help them learn more about how NovoLog affects you. If needed, they can use this information to adjust your treatment plan.

If you have certain medical conditions, you may not be a good fit for NovoLog. This is a drug-condition interaction. Other factors may affect whether or not you choose to use NovoLog. Talk to your doctor about your health history before you start taking this drug. There are a few factors to consider.

Liver or kidney problems. There’s an increased risk of hypoglycemia (low blood sugar) while taking NovoLog if you have liver or kidney problems. If your doctor determines this drug is a safe treatment option for you, they may adjust your dose more often. They may also recommend frequent monitoring of your blood sugar levels.

Allergic reaction. If you’ve had an allergic reaction to NovoLog or any of its ingredients, your doctor will likely not prescribe it for you. Ask them about other treatments that might be better options.

Heart failure. Your risk of heart failure can increase if you use NovoLog while taking diabetes drugs called thiazolidinediones. Sudden weight gain may be a sign of fluid buildup and heart failure. Tell your doctor if you take thiazolidinediones or have new or worsening heart failure while taking this drug. They can recommend a safe treatment plan for you.

Hypokalemia (low potassium level). NovoLog can cause you to have a low level of potassium in your blood. Your risk may increase if you have certain other health conditions or take other medications that can lower your potassium level. Low potassium can cause serious heart problems. If it gets too low, you may need to be treated in a hospital. (See “Side effects explained” above for more information.)

Alcohol and NovoLog

You should avoid using NovoLog with alcohol. Alcohol can decrease NovoLog’s ability to lower your blood sugar. Drinking too much alcohol can cause side effects such as There is a lot of There is a lot of There is a lot of There is a lot of diarrhea…. and There is a throbbing head., which are also side effects of NovoLog. Using the two together can worsen these side effects.

Talk to your doctor about the amount of alcohol that you should not drink.

Pregnancy and breastfeeding while taking NovoLog

The safety of taking NovoLog while pregnant is unknown. But it’s important to manage your blood sugar if you have diabetes, especially during pregnancy. Talk with your doctor about safe ways to manage your blood sugar level if you’re pregnant or planning to become pregnant.

It is not known if the drug can pass into human breast milk or if it will affect a child who is breastfed. Talk to your doctor about the safest ways to feed your baby during your treatment.

If you have type 1 or type 2 diabetes, talk with your doctor to see if NovoLog is right for you. This drug is known to cause several common side effects. These are usually mild, but serious side effects can happen. Your doctor can provide you with more information. A few questions you might want to ask include:

  • Will my treatment with NovoLog be stopped if I have severe side effects?
  • Will my side effects from NovoLog worsen if I have liver or kidney problems?
  • Does NovoLog have more serious side effects than other kinds of insulin drugs?

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Are NovoLog’s side effects different if it’s used to manage blood sugar levels in type 1 diabetes versus type 2 diabetes?



Possibly. In studies, people with type 1 diabetes reported some different common side effects while using NovoLog than those with type 2 diabetes.

You may experience different side effects from this drug.

  • You take other drugs.
  • You may have other health conditions.
  • How well is your diabetes being managed?

The most common side effect of insulin drugs, including NovoLog, is hypoglycemia (low blood sugar). Other side effects that were more common based on diabetes type are listed below.

People with type 1 diabetes report common side effects.

People with type 2 diabetes report common side effects.

You should talk to your doctor about the side effects of NovoLog.

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.