Insulin is a type of hormone which is produced by the pancreas to help our body to properly use the glucose we derive from food we eat. People with diabetes cannot naturally produce enough amounts of insulin or use it properly. This leads to a build up of glucose in the body rather than moving into the cells. High levels of blood sugar can lead to health problems for people with diabetes. However, insulin can be injected under the skin to help people with diabetes reduce the level of blood sugar in their body. NPH insulin is the medication used by patients with diabetes to help manage blood glucose. This type of insulin works by enabling blood glucose to get into the cells so that it can be used for energy by the body. Taken note that insulin NPH is not a cure for diabetes, but helps to control blood sugar levels.

What is NPH insulin (isophane insulin)?

NPH is an acronym for Neutral Protamine Hagedorn. NPH insulin also referred to as isophane insulin, is a type of insulin that is given to patients with diabetes to help control their blood sugar levels. It is taken as an injection and the metabolic effects can be felt within 1 or 2 hours after injection. However, its strongest effect is felt between 6 to 10 hours after injection.

NPH insulin peak times, onset and duration of action

Insulin NPH is considered to be an intermediate acting insulin, which takes 1 to 3 hours before the injection effects are felt. Isophane insulin peaks between 5 and 8 hours after injection but the effects start to cease after 18 to 24 hours.

The duration of action for insulin NPH is 18 to 24 hours. However, when insulin NP is combined with regular insulin, it has a shorter duration of action compared to NPH insulin.


The insulin NPH dosage that your doctor recommends depends on the ability of your pancreas to produce insulin and how well it is used by your body. Your doctor will recommend the right dose, depending on the results obtained after monitoring the values of your blood sugar levels. Other factors like medications used and body weight may affect the dosage your doctor recommends for you. If you have Type 1 diabetes, your doctor may recommend 0.5 to 1 unit/kg/day. It is recommended you take the prescribed units, at least 30 to 45 minutes before having your meal.

How to inject

NPH insulin dose is taken by injecting the medication under the skin. Note that you are not supposed to take insulin isophane by injecting it into your vein. Insulin isophane is usually injected once or twice a day. Always make sure that you useb this medicine as it is prescribed by your doctor so that you can maximize on its benefit. Dosage adjustment may be required if the brand or species of insulin are changed. You may require a higher dosage of insulin if you are using it concurrently with other medication with hyperglycemic effects or are obese, stressed or pregnant. A lower dosage may be required if you are exercising, under a weight loss program or are using other drugs concurrently that has hypoglycemic effects. You should not use insulin isophane if you have low blood glucose levels or you are allergic to the ingredients used in the medication.

Side effects

Most of the side effects associated with NPH insulin can be handled while others disappear on their own. If you are worried about the side effects associated with insulin isophane, you should talk to your doctor.

The most common negative effects include

  • Itchy skin rash
  • Wheezing
  • Thickening of skin after injection
  • Low blood sugar
  • Rapid pulse

The severe negative effects include

  • Seizures
  • Blisters forming all over your body
  • Unconsciousness
  • Difficulty in breathing
  • Swelling of the throat or face

People who take insulin isophane may experience other side effects not on this list. In case of any side effects, you should call your doctor for medical advice. Make sure you do not share this medicine with other people even if they have similar symptoms as yours. This is because insulin NPH may be harmful to people who are not prescribed to use it.

How to store

Always check the expiry date of the insulin medications. Do not use it if it has expired. In case you are not using the insulin cartridge, you should store it in the refrigerator until the next use. Insulin should not be exposed to sunlight or kept under extremely high temperature. Store insulin under room temperature, but not freezing. If stored at room temperature of below 30 degrees Celsius, the vial should be thrown away after 30 days. However, don’t dispose the drug in the toilet or sink. If you are not sure, ask your local pharmacist how you are supposed to properly dispose expired medication. Always make sure that the insulin is kept away from children.

When to take

You may need to take insulin NPH if your level of blood sugar is too high. The best time to take this medicine is 30 to 45 minutes before you take a meal. NPH insulin is administered through injection or shots. It can also be taken using an insulin pen. Make sure you rotate the sites of injection to avoid chances ofn lipodystrophy. Never share syringes or insulin pens between patients to avoid transmission of disease.

Mixing NPH with Regular insulin

NPH insulin may be mixed with other faster acting insulin like regular insulin so that it can control better the levels of blood sugar. The two insulin will require to be combined in the syringe. However, since insulin NPH and regular insulin bind when combined, you should not mix them until the time of injection. Before you inject insulin NPH, make sure you mix it. Mix the insulin by rolling the vial between your hands. After mixing NPH with insulin regular, it should be white and cloudy. Don’t use the mixture if it contains crystals, looks thicker than usual or the mixture is discolored. In addition, do not use the insulin if the vial looks frosted or the insulin looks grainy.


Disclaimer: Please note that the contents of this community article are strictly for informational purposes and should not be considered as medical advice. This article, and other community articles, are not written or reviewed for medical validity by Canadian Insulin or its staff. All views and opinions expressed by the contributing authors are not endorsed by Canadian Insulin. Always consult a medical professional for medical advice, diagnosis, and treatment.