What is intermediate-acting insulin (isophane)?

Intermediate-acting insulin is a man made insulin that contains human insulin complex, which delays absorption and prolongs action in the body. Insulin refers to a hormone that is naturally produced by the pancreas to control blood sugar levels. This hormone works by transporting glucose into the body tissues where it is stored and used for energy. Glucose is a form of sugar which is one of the biggest sources of energy. People with diabetes cannot produce insulin naturally. As a result, glucose cannot enter the body cells for energy. This leads to a build up of glucose in the bloodstream. High blood glucose can lead to health complications such as nerve damage and kidney damage. People with diabetes can take intermediate-acting insulin to compensate the action of the natural hormone. This type of insulin analog enables the body to get the insulin it needs for glycemic control.

This type of  insulin is used to control blood glucose levels between meals and overnight. It works by helping the blood glucose get into the cells where it is used for energy. When injected under the skin, it begins to work within 1 to 2 hours and the effects can last from 12 to 18 hours. Intermediate-acting insulin is also known as NPH (Neutral Protamine Hagedorn) or isophane insulin. Insulin isophane is similar to human insulin. NPH insulin can be prescribed together with short acting insulin to help control blood sugar levels in people with diabetes. When administered this way, the two forms of insulin analog will be combined together in an injection pen.

Names of intermediate-acting insulin

Humulin N

Humulin N is a type of intermediate acting insulin that is used to treat type 2 diabetes. Humulin N is available in vials and Humulin N Kwikpen each having 100 units/ ml.

Novolin N

Novolin is an isophane insulin that is injected under the skin to help improve blood sugar levels in people with type 2 diabetes. Novolin N is usually administered using a syringe.

How to take

Isophane is usually injected under the skin, once or twice every day. The dosage is usually determined by your medical condition and response to treatment. Keep checking your blood sugar levels as you take this medication. This will help determine the correct dose of insulin. Before injecting intermediate-acting insulin, clear the injection site using rubbing alcohol. You can inject intermediate acting insulin in the abdomen area, buttocks, thigh and at the back of the upper arm. Avoid injecting the muscle or vein to reduce the risk of hypoglycemia. Before you take insulin isophane gently roll the cartridge between your palm, turning it upside down and right side up, ten times to mix the medication.

Onset, peak and duration

Onset refers to the length of time it takes for insulin to reach the bloodstream and start to lower the blood glucose levels. The peak is the time when the insulin medication is working the best to reduce blood sugar levels. Duration is the time it takes for insulin to continue to lower blood sugar levels. NPH human insulin has an onset of about 1 to 2 hours, while the peak period is 4 to 6 hours and the duration is 12 hours.

Side effects

Taking intermediate acting insulin can result in hypoglycemia, or low blood sugar.

Symptoms of hypoglycemia include

  • rapid heartbeat
  • blurred vision
  • dizziness
  • shakiness
  • sweating
  • headache
  • unexplained fatigue
  • pale skin

Taking insulin with a needle can also cause injection site reactions, with symptoms such as redness, irritation and pain. If these symptoms worsen, call your doctor immediately.


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.