If you have diabetes, your doctor might suggest Humulin N as a treatment option for you.

Humulin N is a medication available from pharmacies with or without a prescription. It’s used to manage blood sugar levels in adults and children with type 1 or type 2 diabetes. You’ll likely use Humulin N long term if you and your doctor agree it’s working well for you.

Diabetes is a chronic (long-term) condition that causes high blood sugar levels. Left untreated, this can damage many parts of your body, including your eyes, kidneys, nerves, and other organs.

The active ingredient in Humulin N is isophane insulin human. (An active ingredient is what makes a drug work.) Isophane insulin human is a kind of biologic (a drug made from parts of living organisms).

Humulin N comes as a liquid solution given by subcutaneous injection (an injection under your skin). It comes in these forms:

  • prefilled single-dose KwikPen
  • multiple-dose vial

For more information about Humulin N, including details about its uses, talk with your doctor or pharmacist.

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

Note: You don’t need a prescription to buy Humulin N from a pharmacy. But you may prefer to get one if you have insurance that covers all or part of your medication costs. Either way, be sure to talk with your doctor before using Humulin N.

Some people may experience mild to serious side effects during their Humulin N treatment. Examples of commonly reported side effects include:

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

These aren’t the only side effects Humulin N may cause. And not everyone who uses Humulin N will have side effects.

Read on to learn more about some of the mild to serious side effects this drug may cause.

Like most drugs, Humulin N can cause mild side effects. Examples that have been reported 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. But if you have symptoms that are ongoing or bother you, talk with your doctor or pharmacist. And do not stop Humulin N treatment unless your doctor recommends it.

Humulin N 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 side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with Humulin N, visit MedWatch.

Serious side effects can occur during Humulin N treatment. These include:

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

Of those listed above, hypoglycemia (low blood sugar) is the more common side effect.

If you develop serious side effects during your treatment with 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.

Learn more about some of the side effects Humulin N may cause.

Low blood sugar

Humulin N may cause your blood sugar levels to become too low. This is called hypoglycemia. Every drug used to treat diabetes can cause low blood sugar. It’s the most common side effect of drugs that contain insulin. It can be mild to serious but is usually mild when it does happen.

Symptoms of mild low blood sugar can include:

In rare cases, low blood sugar caused by Humulin N can be severe. Your risk of this increases if you:

Symptoms of severe low blood sugar can include:

In extreme cases, severe low blood sugar can also result in death.

What might help

Throughout your Humulin N treatment, you’ll check your blood sugar levels by pricking your finger and using a blood glucose monitor. Your doctor will advise you on how often you should do this.

Before starting treatment, talk with your doctor about what to do if your blood sugar levels become too low. Mild low blood sugar can often be treated at home using quick-acting carbohydrates, such as:

  • glucose (sugar) tablets
  • 1/2 cup of juice or regular (non-diet) soda
  • 1 tablespoon of honey
  • three or four pieces of hard candy

For severe low blood sugar, your doctor may prescribe glucagon. This is a drug used to quickly increase blood sugar levels when they become dangerously low.

Talk with your doctor about your treatment plan in case you have low blood sugar with Humulin N. But if you’re having symptoms of severe low blood sugar or symptoms that feel life threatening, call 911 or go to the nearest emergency room.

Injection site reaction, including thickened skin or skin pits

You’ll give yourself doses of Humulin N by subcutaneous injection (an injection under your skin). This can cause injection site reaction as a side effect. This is a side effect that occurs where you inject the drug. It’s not known how often this side effect occurred in studies.

Injection site reaction caused by Humulin N can include:

  • bleeding or bruising
  • itchy skin
  • pain
  • skin pits or lumps
  • thickened skin
  • skin reddening or discoloration
  • swelling

What might help

The best way to lower your risk of injection site reaction is to change the site where you inject the drug.

Injection sites include the:

  • belly
  • buttocks
  • thighs
  • upper arms (triceps)

Do not use the same spot for each injection. Try to inject the dose into a different area of skin each time, even if you use the same body part. (For example, if you injected your last dose on the right side of your thigh, it’s okay to inject your next dose on the left side of that same thigh.)

You should also avoid injecting Humulin N into skin that is:

  • bruised
  • damaged or scarred
  • hard or scaly
  • tender
  • thickened, lumpy, or pitted

Talk with your doctor or pharmacist if you have injection site reactions that bother you. They can review your injection technique and see if there’s something you could do differently to help reduce your symptoms. They may also suggest that you stop Humulin N and try a different treatment option.

Low blood potassium levels

Humulin N can cause hypokalemia (low blood potassium levels) as a side effect. While it’s not known exactly how often this occurred in the drug’s studies, it isn’t thought to be common.

A low blood potassium level is a risk with all drugs containing insulin, including Humulin N. In most cases, this condition (when it’s caused by insulin) isn’t serious and can be treated with medication. But if it’s left untreated, over time it can cause serious problems, such as:

It can even cause death in extreme cases.

Symptoms of low blood potassium levels can include:

What might help

Before you start Humulin N treatment, your doctor will review your medical history for risk factors of low blood potassium. Taking certain drugs that affect potassium levels can put you at higher risk of this side effect. If your doctor determines you’re at high risk, they may decide to monitor your potassium level more closely using blood tests. But it’s also important to talk with your doctor if you think you have symptoms of hypokalemia.

If you develop low blood potassium during treatment with Humulin N, your doctor will determine the best remedy for this side effect. They may prescribe a drug that will help increase your potassium levels. Or they may have you stop Humulin N and try a different diabetes treatment option.

Allergic reaction

Like most drugs, Humulin N can cause an allergic reaction in some people. This side effect was reported in studies, although it’s not known how often it occurred.

Symptoms can be mild to 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. They may suggest an over-the-counter oral antihistamine, such as Benadryl (diphenhydramine), or a topical product, such as hydrocortisone cream, to manage your symptoms.

If your doctor confirms you’ve had a mild allergic reaction to Humulin N, 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’ve had a serious allergic reaction to Humulin N, they may have you switch to a different treatment.

Keeping track of side effects

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

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

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

Can using a Humulin N KwikPen cause different side effects than using a syringe?

Side effects aren’t expected to differ based on whether you use the KwikPen or a syringe for your dose of Humulin N. Differences weren’t reported in the drug’s studies.

Both forms of Humulin N are given by subcutaneous injection (an injection under your skin). Both can cause an injection site reaction, such as skin pits and thickening of the skin. This is covered in more detail in the “Side effects explained” section below.

If you’d like to know more about using Humulin N KwikPens or vials, talk with your doctor or pharmacist. You can also view detailed instructions in the drug’s labeling.

Can Humulin N cause any long-term side effects?

No, Humulin N insulin isn’t known to cause any long-term side effects.

Long-term side effects could refer to those that begin:

  • during treatment and continue for a long time (possibly after treatment ends)
  • after you’ve taken the drug for a long time
  • after your treatment is finished

But none of these were reported in Humulin N’s studies.

Talk with your doctor or pharmacist if you have questions about long-term effects of this drug.

Can Humulin N cause heart failure?

It depends. On its own, Humulin N didn’t cause heart failure as a side effect in studies.

But taking certain other diabetes medications together with Humulin N may increase your risk of heart failure. These drugs are known as thiazolidinediones. Examples include:

For this reason, be sure you tell your doctor and pharmacist about all medications you take before you begin treatment with Humulin N. They can review your medications for any possible interactions with this drug and help determine the best treatment plan for you.

Humulin N 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 starting Humulin N. Below are a few factors to consider.

Kidney or liver problems. It’s usually safe for people with kidney or liver problems to use Humulin N. But your doctor may want to monitor your kidney or liver function closely in these situations. This is because small changes in liver or kidney function can change how your body reacts to Humulin N. If you have kidney or liver problems, your doctor may need to frequently change your Humulin N dose.

Heart problems, including heart failure. Be sure to tell your doctor if you have heart problems, especially heart failure, before you begin Humulin N treatment. Using certain other diabetes medications together with Humulin N may increase your risk of heart failure. These drugs are known as thiazolidinediones. Examples include Actos (pioglitazone) and Avandia (rosiglitazone). Your doctor can help determine the safest diabetes treatment plan for you. If you take a thiazolidinedione drug, your doctor may have you stop it when you start Humulin N.

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

Alcohol and Humulin N

If you drink alcohol, it’s best to talk with your doctor about how much (if any) is safe to drink during Humulin N treatment.

Alcohol can increase your risk of certain side effects from Humulin N, including:

Alcoholic beverages can also affect your blood sugar levels, which can cause Humulin N not to work as well.

Your doctor can tell you more about the risks of drinking alcohol with Humulin N.

Pregnancy and breastfeeding with Humulin N

Humulin N is thought to be safe for use during pregnancy. High blood sugar levels, which Humulin N is used to manage, are known to increase the risk of complications during pregnancy. These complications include harm to the pregnant person and loss of pregnancy.

There aren’t any known safety issues with breastfeeding during treatment with Humulin N.

If you have concerns about treatment with this drug while pregnant or breastfeeding, talk with your doctor or pharmacist.

Like most medications, Humulin N can cause side effects. Some side effects, like low blood sugar, are more common than others. Most of the side effects this drug can cause are the same as those caused by other insulin drugs.

Before starting Humulin N treatment, talk with your doctor. Ask them questions that help you feel comfortable about the risks and benefits of this treatment. Some examples to help get you started are:

  • How do my eating habits affect my risk of side effects from this drug?
  • Are there ways to help me manage side effects from Humulin N?
  • If I develop kidney problems, how will that affect my risk of side effects from Humulin N?

If you have type 2 diabetes, consider signing up for Healthline’s online newsletter to learn tips for managing your condition. Or check out Bezzy T2D, where you can get and share advice with others living with this condition.

Q:

Is it safe for adults ages 65 years and older to use Humulin N?

Anonymous

A:

Yes, Humulin N is safe for older adults (people ages 65 years and older). But older adults may be at higher risk of hypoglycemia (low blood sugar) from treatment with Humulin N or any other insulin drug. This is because the way our bodies handle and respond to drugs like Humulin N changes as we age.

For example, older adults are more likely to have kidney or liver problems. These problems can increase your risk of side effects from Humulin N or other insulins. Older adults are also more likely to take more medications, some of which can increase their risk of side effects from Humulin N.

If you’re age 65 years or older, your doctor may prescribe a lower Humulin N dose or monitor you more closely for side effects.

The Healthline Pharmacist TeamAnswers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.
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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.