Humulin N (isophane insulin human) is a brand-name prescription medication. The Food and Drug Administration (FDA) has approved it to improve blood sugar levels in adults and children with type 1 or type 2 diabetes.

If Humulin N works to treat your diabetes, your doctor will likely recommend that you take it long term.

Here are some fast facts about Humulin N:

  • Active ingredient: isophane insulin human, which is a biologic
  • Drug class: intermediate-acting insulin
  • How it’s given: as a subcutaneous injection by using either:
    • multiple-dose vial with insulin syringes
    • KwikPen with pen needles

As with other drugs, side effects of Humulin N can occur. Read on to learn about potential common, mild, and serious Humulin N insulin side effects. For a general overview of Humulin N, talk with your doctor or a pharmacist. You can also see this article about how Humulin N is used for diabetes.

Humulin N can cause certain side effects (also called adverse 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 Humulin N in clinical trials:

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

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

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

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

Humulin N may cause serious side effects. In most cases, serious side effects are not common, but they still may occur. So, it’s important that you are aware of possible serious side effects so you can report them to your doctor.

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

If you develop serious side effects while taking Humulin N, 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 the “Side effect specifics” section below

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

Are the Humulin N KwikPen side effects different from those caused by the syringe?

No, you are likely to have the same side effects from the Humulin N KwikPen that you would have from the Humulin N syringe. This is because both drugs contain the same active ingredient, isophane insulin human. In fact, the only difference between the syringe and the KwikPen is the injection device that the drug comes in. Since both forms of Humulin N involve injection, they both may cause injection site reactions.

In some cases, the syringe or the KwikPen may be easier for you to use. Talk with your doctor or pharmacist about the best form of Humulin N for you.

How long does Humulin N last in the body?

The amount of time Humulin N lasts in the body varies based on the individual and how their body breaks down the drug. On average, the half-life of Humulin N is believed to be just under 4 and a half hours. A medication’s half-life is the amount of time it takes for half of the drug to be removed from your body.

However, the half-life of Humulin N can vary from 1 hour to 84 hours, depending on the person. Because of this range, your doctor will personalize the dosing of Humulin N specifically for you.

Can Humulin N cause diarrhea?

No, diarrhea is not a side effect that people taking Humulin N reported in clinical trials. So if you experience diarrhea while you’re taking Humulin N, talk with your doctor.

Other diabetes medications, such as Fortamet (metformin), may cause diarrhea. Your doctor can help you determine the cause of your diarrhea and the best way to treat it.

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

Hypoglycemia (low blood sugar)

Humulin N may cause hypoglycemia, or low blood sugar. Low blood sugar is a common side effect in people taking Humulin N. Even though low blood sugar may be common, it can be severe or life threatening.

Symptoms of low blood sugar may include:

What you can do

If you notice any symptoms of low blood sugar, tell your doctor right away so they can recommend treatment. Many times, your doctor will discuss how to treat low blood sugar before you start treatment with Humulin N.

In most cases, your doctor will recommend that you check your blood sugar levels and use treatment if your levels become too low. The American Diabetes Association recommends treating low blood sugar levels by eating 15 grams of carbohydrates. Then, you should wait 15 minutes and retest your blood sugar levels. If they are still too low, you may need to repeat this process.

Some examples of foods that contain 15 grams of carbohydrates include:

  • glucose tablets
  • 4 ounces of juice or non-diet soda
  • 1 tablespoon of sugar or honey
  • hard candies

If you have low blood sugar levels often, talk with your doctor. In some cases, your doctor may adjust your dosage of Humulin N or other diabetes medications you take to prevent this side effect from occurring.

To learn more about Humulin N’s dosage, see this article.

Injection site reaction

You may have an injection site reaction from taking Humulin N. Injection site reactions are side effects that occur in the area where you inject your dose of Humulin N. This side effect was commonly reported in Humulin N’s clinical trials.

Examples of possible injection site reactions include skin redness or discoloration, swelling, and pain.

What you can do

It’s important that you change injection sites with each Humulin N injection. Doing so can help prevent certain side effects, such as injection site reactions.

If you notice injection site reactions during your treatment with Humulin N, talk with your doctor. They may be able to recommend ways to prevent these side effects from occurring.

Swelling of your arms or legs

Humulin N may cause edema (swelling due to fluid buildup) of the arms or legs. This was a common side effect in clinical trials of Humulin N.

What you can do

It’s possible for Humulin N to increase your risk of heart failure if you’re taking it in combination with another type of diabetes drug called a thiazolidinedione. Heart failure may also cause swelling of the arms or legs.

If you notice swelling of your arms or legs during your treatment with Humulin N, talk with your doctor. They can help determine exactly what is causing your swelling and how to treat it. In some cases, your doctor may recommend taking another medication to decrease this side effect.

Weight gain

You may experience weight gain during your treatment with Humulin N. Weight gain was a common side effect in clinical trials of Humulin N. In fact, weight gain is a common side effect of any insulin treatment.

What you can do

If you notice unintentional weight gain during your treatment with Humulin N, tell your doctor. In some cases, weight gain can be due to other side effects, such as swelling of your arms or legs, or heart failure. You may be at an increased risk of heart failure if you’re taking Humulin N in combination with another type of diabetes drug called a thiazolidinedione.

Your doctor can help you determine what is causing your weight gain and how best to treat it. They may also be able to recommend changes in your diet or exercise to help decrease weight gain.

Allergic reaction

As with most drugs, Humulin N can cause an allergic reaction in some people.

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 they can determine whether you should keep taking Humulin N. 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 Humulin N. 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:

Liver problems. Tell your doctor if you have any liver problems before starting treatment with Humulin N. Liver problems may increase your risk of low blood sugar levels while you’re taking Humulin N. Due to this risk, your doctor may monitor you more often or decrease your dose of Humulin N to prevent low blood sugar from occurring.

Kidney problems. If you have any kidney problems, tell your doctor before starting treatment with Humulin N. Kidney problems can increase your risk of low blood sugar levels during your treatment with Humulin N. Your doctor may recommend more frequent monitoring or a lower dose of Humulin N to prevent low blood sugar.

Heart failure or heart problems. If you have heart failure or heart problems, tell your doctor before starting treatment with Humulin N. If you’re taking another type of diabetes drug called a thiazolidinedione with Humulin N, you may be at an increased risk of heart failure or worsening heart problems. Your doctor can help you determine if Humulin N is safe for you to take if you have heart failure or other heart problems.

Thiazolidinediones (TZDs). If you’re taking Humulin N in combination with another type of diabetes drug called TZDs, tell your doctor before starting Humulin N. TZDs, when taken along with Humulin N, can increase the risk of fluid buildup and heart failure. Due to this risk, your doctor may monitor you more often for symptoms of heart failure. In some cases, they may recommend a different treatment option for you.

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

Hypoglycemia. If you currently have hypoglycemia (low blood sugar levels), you should not inject a dose of Humulin N. This medication works to decrease your blood sugar levels. If you already have low blood sugar levels, taking Humulin N can cause your blood sugar to become even lower. This can be very serious or even life threatening. Tell your doctor if you have low blood sugar levels often. In some cases, they may need to adjust your dose of Humulin N.

Lipodystrophy. It’s possible to develop lipodystrophy (injection-related scarring under your skin) as a side effect of using Humulin N. It’s important that you do not inject additional doses into the area until your symptoms have been managed. Doing so could result in hyperglycemia (high blood sugar). You should use a different site for injecting Humulin N doses until symptoms of lipodystrophy go away.

Alcohol with Humulin N

There are no known interactions between Humulin N and alcohol. However, alcohol may affect your blood sugar levels. Humulin N works to help improve your blood sugar levels, so drinking alcohol may make your blood sugar levels harder to manage.

If you drink alcohol, talk with your doctor about the amount that’s safe to drink while taking Humulin N.

Pregnancy and breastfeeding while taking Humulin N

Humulin N is likely safe to use while pregnant or breastfeeding. Although there haven’t been any studies done specifically on the effects of Humulin N during pregnancy, many studies have shown that human insulin, such as Humulin N, is safe to use during pregnancy.

There hasn’t been an increased risk of miscarriage or congenital anomalies (also known as birth defects) when human insulin is used during pregnancy. In fact, uncontrolled diabetes can increase the risk of miscarriage and congenital anomalies.

It’s also likely safe to breastfeed while using Humulin N. The drug may pass into breast milk. However, no negative effects in a breastfed child have been reported.

Talk with your doctor about your treatment options for diabetes if you’re pregnant, planning to become pregnant, or breastfeeding.

You may experience side effects during your treatment with Humulin N. However, most side effects are mild. If you’d like to learn more about Humulin N, 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.