NPH Insulin, What is it? How To Use It, Side Effects, Help and Advice

Posted September 3, 2019 by Michael Chamberlain - See Editorial Guidelines

Here’s where you can find out all the information you need to know regarding NPH Insulin. How to use it, benefits, side effects, knowing the symptoms if you feel you might have overdosed, and much more.

But, for those that have not come across it before, let’s start with a quick takeaway answer, then we can get into more detail.

What Is NPH Insulin? Neutral Protamine Hagedorn (NPH) also known as Isophane insulin is used to improve blood sugar control in adults and children with diabetes. It’s an intermediate-acting insulin that starts to work within 2-4 hours after injection. The insulin peaks in 4-12 hours and works for 12-18 hours. 

For those unaware of the background on insulin, it is normally produced naturally by the pancreas. Insulin products are produced by pharmaceutical manufacturers and are categorized based on the time of onset, the peak, and how long they last in the body’s system. They work to lower blood sugar (glucose) levels in patients that have diabetes.

With that background set up, let’s get into more details about this insulin.

NPH insulin

How To Use NPH Insulin

Firstly, read any instructions provided to you along with the medications and follow accordingly. If you don’t clearly understand the instructions for proper usage, ask your doctor or pharmacist regarding anything.

Your care provider will show you exactly where to inject the NPH insulin. NPH insulin is usually injected under the skin two times a day.  It is crucial that patients rotate their injection sites. Injecting insulin in the same area of skin repeatedly without allowing the skin to heal can lead to injection site reactions. Overuse of an injection site can lead to scar tissue and hardened skin, causing pain and decreased insulin absorption. 

When injecting, check if your insulin mixture looks cloudy after mixing. If the mixture looks clear or you find particles on it then don’t use it. Call your pharmacist to arrange some new medication. 

If you’re using an injection pen, use only the pen that comes along with the insulin. Do not give NPH insulin with an insulin pump. Also, make sure to attach a new needle before each use. Never transfer the insulin from a pen into a syringe.

Most importantly never share a used pen or syringe with another person, even if the needle has been changed. This is because sharing as such can cause the risk of infections or diseases passing from one person to another.

Things To Watch For When Using NPH Insulin 

nph insulin

As mentioned, NPH insulin aims at regulating blood sugar levels. So, it’s important for you to watch for symptoms that indicate a rise or fall in blood sugar levels. 

Low blood sugar (hypoglycemia) can happen to anyone with diabetes easily. Symptoms of low blood sugar include sweating, hunger, headache, nausea, feeling shaky, dizziness, and irritability.

As NPH insulin acts after two to four hours, you may need to take some fast-acting source of sugar with you such as fruit juice, hard candy, crackers, raisins, or non-diet soda. However, make sure your family or friends who are around you know how to inject NPH insulin, in case of emergencies. 

You should also watch for signs of high blood sugar (hyperglycemia). Common symptoms of high blood sugar include headache, tiredness, blurred vision, increased thirst, or urination. 

It’s also important to remember that blood sugar can be affected by exercise, alcohol use, surgery, illness, and skipping meals. So, it’s important to watch for these things while taking NPH insulin. You should also ask your doctor regarding any NPH insulin dosage schedule that you plan on changing.

Always keep in mind that NPH insulin is only part of a complete treatment program. Meaning the insulin alone cannot help control blood sugar levels, you may have to watch for the things mentioned above, including your diet, weight, and exercise patterns according to your doctor’s instructions. These efforts added with the NPH insulin only can give you effective blood sugar control, whereas just the usage of the insulin may show only temporary results. 

Regarding the effective use of this insulin, let’s take a look at some precautions when using this insulin.

Precautions To Be Taken While Using NPH Insulin

Before using this medication or when the doctor prescribes you this medication, make sure you inform your doctor regarding all your allergies. Especially regarding allergies to any other type of insulin. 

Also, make sure to tell your doctor if you also take pioglitazone or rosiglitazone (sometimes contained in combinations with glimepiride or metformin). This is because NPH insulin may contain inactive ingredients that can cause allergic reactions or other related problems. 

At the same time tell your doctor or pharmacist your medical history, especially of cases such as thyroid problems, liver disease, adrenal/pituitary gland problems, kidney disease, and low levels of potassium in your blood (hypokalemia). Before undergoing surgery, tell your doctor all about the NPH insulin you have been using along with other prescription drugs, nonprescription drugs, and herbal products you use.

Never give NPH insulin to children without advice from a physician, and don’t use this medication if you tend to experience episodes of low blood sugar (hypoglycemia). Older adults and children are more sensitive to the side effects of this drug, especially low blood sugar. Also, in case you are traveling across time zones, consult your doctor regarding how to adjust the insulin schedule. You might as well take extra insulin and related supplies with you as a precaution in case of emergencies. 

If you’re pregnant while using NPH insulin, tell your doctor regarding it. This is because pregnancy may cause or worsen diabetes conditions with the use of insulin. So, make sure you discuss a plan with your doctor on how to control blood sugar while pregnant and if it is safe to use the insulin according to your health conditions. The doctor may even change your diabetes treatment during the time of pregnancy that best suits you. Sometimes the doctor may recommend some different insulin dosages during each trimester of pregnancy. 

The same applies to nursing mothers. Consult your doctor about using insulin while breastfeeding. Your insulin dosage may need to change while breastfeeding too. NPH insulin passes into breast milk, but it’s unlikely to cause any health risk to the nursing infant. However, it is highly recommended to consult a doctor regarding this.

After precautions, another thing anybody using NPH insulin has to be cautious about is its correct storage.

Storage Instructions for NPH Insulin 

nph insulin

Make sure you keep the insulin in its original container (The package that the insulin comes in). Keep the original package away from heat and light. Check the product package for storage details and follow accordingly. Different brands have different storage instructions, so make sure you check the details or ask the pharmacist regarding storage details 

Never cool or freeze the insulin or store it near the cooling element in a refrigerator. Also, don’t store the insulin in the bathroom. Throw away the insulin after the expiration date mentioned on the package. Some packages will specify the number of day’s insulin can be stored after opening or after keeping at room temperature.

Store the insulin away from children and pets. Along with storage make sure you follow proper disposal. Never flush down the toilet or pour the insulin into a drain. Properly discard as instructed or consult your pharmacist or local waste disposal company.

Storing instructions may differ based on whether you’ve opened the package or not. So, let’s see this in detail.

Storing Unopened (not in use) NPH Insulin:

  • You can store unopened insulin in the refrigerator until the expiration date. Unopened NPH insulin is refrigerated between 2 and 8 degrees C (36 and 46 degrees F).
  • You can also store your insulin at room temperature. But for this, you might have to follow the instructions provided within the package. When storing it at room temperature, make sure to use it within the number of days specified in the instructions. The benefit of keeping NPH insulin at room temperature is that it would decrease the amount of discomfort during injection.

Storing Opened (in use) NPH Insulin:

  • Never refrigerate an in-use injection pen. An in-use NPH insulin (after opening) should be kept at room temperature below 30 degrees C (86 degrees F). Protect opened insulin from heat and light.
  • An in-use NPH insulin is stable for only a certain number of days. So be sure to throw away the medication not used within the specified time. Usually, opened insulin is thrown away after 14 days of opening. This may differ based on other brands.

    For example, if you’re using Humulin N brand vials, the open insulin has to be thrown out after 31 days. And if you’re using Novolin N brand vials, the open insulin has to be thrown out after 42 days.
  • Also, after using open insulin it’s better stored in a suitable safe container.

NOTE: The above explanation is only a summary of storage instructions. The above explanation may not cover all possible storage guidelines. If you have any more questions regarding the insulin, talk to your doctor, health care provider, or pharmacist.

Another common question many have with NPH insulin or any insulin is on missing the dose. Let’s look at that as well.

What To Do When You Miss A Dose

If you miss a dosage, use the insulin as soon as you can. However, if you missed the dosage when it’s almost time for your next dosage, then it’s better to skip the missed dosage.

When using NPH insulin it becomes very important to follow your insulin regimen exactly. This is because as we said earlier, NPH insulin is an ‘intermediate insulin’ that starts working after a few hours. Make sure you ask your doctor ahead on what and what not to do if you miss a dose of insulin.

 At the same time get your prescription refilled before you run out of medication completely. If you’re out of town, then check this article on filling a prescription for further details.

The other common question that comes along with missing a dose is overdosing. Let’s take a look at what you can do when you overdose.

What To Do When You Accidentally Overdose on NPH Insulin

If you accidentally overdose on NPH insulin, seek immediate medical attention right away or call the poison helpline at 1-800-222-1222.

If you’re not sure, then you’ll need to understand the symptoms of overdose so you can recognize it. Here’s a list of the main symptoms. If you are suffering from any of these then look to consult a doctor as soon as possible. Even if you haven’t overdosed, it’s still better to be safe.

  • Blurred Vision
  • Confusion
  • Drowsiness
  • Trouble Speaking
  • Muscle Weakness
  • Clumsy or Jerky Movements
  • Seizures (Convulsions)
  • Loss of Consciousness
  • Sweating
  • Shakiness
  • Fast Heartbeat
  • Difficulty Breathing

Now let’s move on to the side effects of NPH Insulin

NPH Insulin Side Effects

There are side effects for this drug that you may have to be conscious of. Some of the common symptoms of a side effect include signs of insulin allergy.

Symptoms such as redness, swelling, itching, or rash over the skin where the insulin was injected may be a sign of possible side effects. Even trouble in breathing, chest tightness, feeling of passing out, or swelling in your throat or tongue are a few other symptoms of possible NPH insulin side effects.

You may have to call your doctor immediately if you experience the following. 

  • Fluid retentions, which may include weight gain, swelling in your hands or feet, feeling short of breath.
  • Low potassium, which may include leg cramps, fluttering in your chest, increased thirst or urination constipation, irregular heartbeats, numbness or tingling, muscle weakness, or limp feeling.

However, this may not be the complete list of all possible side effects of NPH insulin. Of course, the side effects vary based on the different people and their relative health conditions.

To finish up here let’s talk about NPH insulin interaction with other drugs. NPH drug interactions are important to be aware of if you’re using other medications in parallel. This is because NPH insulin does show some interactions with other drugs. 

Drug Interactions with NPH Insulin

NPH insulin interactions with other drugs may increase the risk of serious side effects. Make sure you keep a list of all the medications you’re currently using with NPH insulin (This includes prescription/nonprescription drugs, vitamins, and herbal products).

Share these details with your doctor or pharmacists and seek advice about the intake of NPH insulin along with them. Never start, stop, share, or change any dosage of the meds you were using before the NPH insulin without your doctor’s advice. The common drugs that may interact with NPH insulin include repaglinide and rosiglitazone.

Some drugs may disturb the symptoms you would feel when you need the insulin dose immediately. For example, the use of beta-blocker medications (such as metoprolol, propranolol, glaucoma eye drops such as timolol) can prevent the fast/pounding heartbeat that one usually feels when your blood sugar falls too low (hypoglycemia).

This may cause one not to find the necessity to use NPH insulin – even if the blood sugar level is going beyond risky levels.

In Closing…

We hope this has been useful, NPH Insulin is a powerful medication and needs to be respected and used within proper guidelines. Always consult your doctor if you have any doubts whatsoever!

If you suffer from diabetes and you’re having trouble affording any of the medications you’ve been prescribed, fill out an enrollment form, and we’ll be happy to help.

What is NPH insulin?

NPH (Neutral Protamine Hagedorn) insulin is an intermediate-acting insulin that may also be known as isophane insulin.

How long does it take for NPH insulin to peak?

NPH insulin starts to work within 1-2 hours, peaks between 4-6 hours after injection, and lasts about 12 hours.



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