NovoLog (insulin aspart) is a brand-name prescription medication. The Food and Drug Administration (FDA) has approved it to manage blood sugar levels in adults and children with either type 1 or type 2 diabetes.

Novolog is typically used long term if you and your doctor agree it’s safe and working well for you.

Here are some fast facts about NovoLog:

As with other drugs, NovoLog can cause side effects. Read on to learn about potential common, mild, and serious side effects. For a general overview of NovoLog, including details about its uses, see this article.

NovoLog 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 NovoLog in clinical trials:

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

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

Mild side effects that have been reported with NovoLog 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 while taking NovoLog and want to tell the FDA about it, visit MedWatch.

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

NovoLog may cause serious side effects, but these aren’t common. If you have certain medical conditions, you may be at increased risk for serious side effects from NovoLog. To learn more, see the “Precautions” section below.

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

If you develop serious side effects while taking NovoLog, 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:

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

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

What side effects should I expect when using the NovoLog FlexPen?

This article discusses the side effects of all forms of NovoLog, including the NovoLog FlexPen. This means that the expected side effects will be the same whether you use a NovoLog insulin pen or a vial of NovoLog together with insulin needles and syringes.

If you have questions about side effects from a specific form of NovoLog, talk with your doctor.

What are the side effects of using too much NovoLog?

Taking too much of a medication such as NovoLog can cause side effects, some of which may be serious. This is known as an overdose.

Using too much NovoLog may cause hypoglycemia (low blood sugar) or hypokalemia (low blood potassium levels). Rarely, low blood sugar can be severe or even life threatening.

To learn more, see the “Side effect specifics” section below. You can also talk with your doctor or pharmacist to learn more about these side effects.

To avoid taking too much NovoLog, make sure you give yourself your doses exactly as your healthcare professional tells you. If you’re confused or having trouble using NovoLog, contact your doctor or pharmacist. They can make sure you know how to give yourself NovoLog doses correctly.

How do side effects of NovoLog compare with NovoLog 70/30?

NovoLog and NovoLog 70/30 are very similar medications. They both contain insulin aspart as the active ingredient. However, NovoLog 70/30 contains two types of insulin aspart. One type works in your body for slightly longer than regular insulin aspart.

So, you will use NovoLog 70/30 in a slightly different way to NovoLog. However, these two medications can cause very similar side effects, including low blood sugar, low blood potassium levels, and injection site reactions.

To learn more about how NovoLog and NovoLog 70/30 compare, talk with your doctor or pharmacist.

Learn more about some of the side effects that NovoLog may cause. To find out how often side effects occurred in clinical trials, see the prescribing information for NovoLog.

Weight gain

Similarly to other types of insulin, Novolog can cause weight gain. It’s not known how common this side effect occurred in clinical trials of the drug, or how much weight was gained on average.

Weight gain may also be due to fluid retention (swelling), which is another side effect that Novolog may cause. To learn more, see “Fluid retention” below.

Certain medications may cause fluid retention and weight gain if you take them in combination with NovoLog. See the “Precautions” section below to learn more.

What you can do

If you’re concerned about weight gain while using NovoLog, talk with your doctor. Together, you and your doctor can develop ways to maintain a weight that’s healthy for you. Typically, people do not need to stop using NovoLog due to weight gain.

Hypoglycemia

Hypoglycemia (low blood sugar) is the most common side effect caused by all insulin drugs, including NovoLog.

NovoLog is used to manage blood sugar levels in adults and children with either type 1 or type 2 diabetes. Diabetes causes blood sugar levels to become too high. NovoLog works to lower blood sugar levels. However, these medications can cause blood sugar levels to drop too low, causing hypoglycemia.

Usually, hypoglycemia from NovoLog is mild. Symptoms of mild hypoglycemia can include:

However, NovoLog can also cause severe hypoglycemia in rare cases. Severe hypoglycemia can be life threatening and may require hospitalization if it isn’t treated right away. Your risk for severe hypoglycemia from NovoLog is higher if you skip meals. (You should give yourself your dose of NovoLog about 5 to 10 minutes before a meal).

Symptoms of severe hypoglycemia can include:

What you can do

If your doctor prescribes NovoLog for you, you and your doctor should make a plan for how you’ll handle hypoglycemia if it happens. You should regularly check your blood sugar while using NovoLog according to your doctor’s instructions.

It’s possible to treat mild hypoglycemia by immediately eating or drinking glucose (simple sugar). You should try to take in at least 15 grams of sugar. Examples of good sources for simple sugar include:

  • ½ cup fruit juice, such as orange or apple juice
  • 3 to 4 glucose tablets
  • 1 tablespoon of sugar or honey
  • ½ cup of non-diet soda

Severe hypoglycemia needs immediate treatment. For treating severe hypoglycemia, your doctor may prescribe an emergency drug called glucagon. This is a medication given by injection or nasal spray if your blood sugar becomes severely low and you can’t take sugar by mouth. You’ll need someone else to give you this treatment, such as a friend, partner, or coworker who knows how to recognize and treat severely low blood sugar. Examples of glucagon medications include GlucaGen and Baqsimi.

If you have hypoglycemia symptoms that feel life threatening, immediately call 911 or seek emergency medical help. Do not attempt to drive yourself to the hospital if you are having severe hypoglycemia symptoms.

Fluid retention

Similarly to other types of insulin, NovoLog may cause fluid retention (swelling) as a side effect. This is one of the more common side effects caused by NovoLog.

Fluid retention happens when there’s a buildup of water in your body. Using insulin drugs such as NovoLog can lead to fluid retention because insulin causes your body to retain (hold on to) more salt than usual. Salt helps regulate the amount of water in your body. Having a higher level of salt in the body will likely cause you to have a higher level of water in the body, too.

Fluid retention caused by NovoLog typically affects your hands, feet, and lower legs.

What you can do

Talk with your doctor if you notice fluid retention while using NovoLog.

In some cases, this side effect goes away with time. This may be the case if your blood sugar levels were previously not managed. Starting treatment with an insulin drug such as NovoLog can cause fluid retention if the drug quickly lowers your blood sugar levels.

But if you have fluid retention that doesn’t go away or bothers you, your doctor may decide it’s best that you stop treatment with NovoLog. In this case, they can discuss other treatment options for your diabetes.

Injection site reactions

You may experience injection site reactions from using NovoLog. These were among the more common side effects reported in the drug’s clinical trials.

Injection site reactions are side effects which occur at the place where you inject your NovoLog doses. (NovoLog comes as a solution for subcutaneous injection).

Injection site reactions that may occur with NovoLog include:

  • itchiness
  • pain
  • skin rash, discoloration, redness, or warmth
  • swelling

What you can do

You can lower your risk for injection site reactions with NovoLog by rotating the place where you inject each dose. You can inject NovoLog doses under the skin of your thigh, abdomen, and upper arm.

Rotating the injection site can help prevent skin irritation, which may help avoid injection site reactions.

If an injection site reaction does occur while you’re using Novolog, keep in mind that most of these reactions go away on their own within hours or a few days. These reactions are typically mild.

But if you develop a reaction that bothers you or won’t go away, let your doctor know. They may want to see your reaction in person to determine if there could be another cause. They may also suggest switching to a different diabetes medication.

Allergic reaction

As with most drugs, NovoLog can cause an allergic reaction in some people. Mild, local reactions at the injection site (such as skin rash) were common in clinical trials. However, in rare cases, the drug can cause more serious allergic reactions, including anaphylaxis.

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

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 taking NovoLog. However, if your symptoms are serious and you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Be sure to talk with your doctor about your health history before you take NovoLog. This drug may not be the right treatment for you if you have certain medical conditions or other factors that affect your health. These are considered drug-condition or drug-factor interactions. The conditions and factors to consider include:

Heart failure. Certain diabetes medications called thiazolidinediones can worsen heart failure symptoms if they’re used in combination with NovoLog. Examples of thiazolidinediones include Actos (pioglitazone) and Avandia (rosiglitazone). Be sure to tell your doctor about all medications you take before you start treatment with NovoLog. If you use NovoLog in combination with a thiazolidinedione, your doctor may have you stop taking one drug or another if your heart failure symptoms worsen during treatment.

Kidney or liver problems. People with kidney or liver problems may be at higher risk for hypoglycemia (low blood sugar) from using NovoLog. Examples of these problems include alcoholic liver disease and chronic kidney disease. It’s usually safe for people with these problems to use NovoLog. However, your doctor may want to closely monitor your blood sugar levels during treatment.

Hypokalemia (low blood potassium level). All insulins, including NovoLog, can cause hypokalemia (low blood potassium levels). Using NovoLog may worsen your condition if your potassium levels are already low. Your doctor will likely monitor your potassium levels while you use NovoLog.

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

Alcohol with NovoLog

Talk with your doctor about whether it’s safe for you to drink alcohol while using NovoLog.

Alcohol and NovoLog can lower blood sugar levels. If you combine the two, you may raise your risk for hypoglycemia, which can be severe.

Talk with your doctor about whether it’s safe for you to drink alcohol while using NovoLog. They can also suggest how much (if any) may be safe for you to drink during treatment.

Pregnancy and breastfeeding while taking NovoLog

The American Diabetes Association recommends insulin, including NovoLog, as the preferred treatment for managing blood sugar levels in pregnant people with diabetes.

Data from clinical trials have not shown harmful effects of NovoLog in pregnancy. However, high blood sugar levels are known to raise the risk for pregnancy complications.

It’s not known whether NovoLog passes into human breast milk, or if it could cause side effects in a breastfed child.

If you’re pregnant, planning to become pregnant, or breastfeeding, talk with your doctor about the safest treatment option for your condition. They can recommend alternative feeding options for your child.

It’s possible to have mild or severe side effects from using Novolog, although severe side effects aren’t common in clinical trials.

Insulins, such as NovoLog, can cause hypoglycemia (low blood sugar) which is usually mild but can be severe in rare cases. NovoLog, like other insulins, commonly causes weight gain and fluid retention (swelling) as well.

If you’d like to learn more about NovoLog, talk with your doctor or pharmacist. They can help answer any questions you have about side effects from taking the drug.

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

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.