Insulin NPH

Reviewed on 7/20/2022

What Is Insulin NPH and How Does It Work?

Insulin NPH is an over-the-counter medication used to treat Type 1 and Type 2 Diabetes Mellitus.

  • Insulin NPH is available under the following different brand names: Humulin N, Novolin N.

What Are Side Effects Associated with Using Insulin NPH?

Common side effects of Insulin NPH include:

  • low blood sugar, 
  • weight gain, 
  • swelling in the hands or feet, 
  • itching, 
  • mild skin rash, and
  • thickening or hollowing of the skin at the injection site
  • redness or swelling at the injection site

Serious side effects of Insulin NPH include: 

  • itchy skin rash over the entire body, 
  • trouble breathing, 
  • chest tightness, 
  • lightheadedness
  • swelling of the tongue or throat, 
  • weight gain, 
  • swelling in hands or feet, 
  • shortness of breath, 
  • leg cramps, 
  • constipation, 
  • irregular heartbeats, 
  • fluttering in the chest, 
  • increased thirst or urination, 
  • numbness or tingling, 
  • muscle weakness, and
  • limp feeling

Rare side effects of Insulin NPH include:

  • none

Seek medical care or call 911 at once if you have the following serious side effects:

  • Severe headache, confusion, slurred speech, arm or leg weakness, trouble walking, loss of coordination, feeling unsteady, very stiff muscles, high fever, profuse sweating, or tremors;
  • Serious eye symptoms such as sudden vision loss, blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights;
  • Serious heart symptoms include fast, irregular, or pounding heartbeats; fluttering in the chest; shortness of breath; sudden dizziness, lightheartedness, or passing out.
This is not a complete list of side effects and other serious side effects or health problems may occur as a result of the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may report side effects or health problems to FDA at 1-800-FDA-1088.

What Are Dosages of Insulin NPH?

Adult and pediatric dosage

Injectable suspension

  • 100 units/mL (3mL)
  • 100 units/mL (10mL)

Type 1 Diabetes Mellitus

Adult dosage

  • Daily maintenance range: 0.5-1 unit/kg/day SC in divided doses
  • Nonobese may require 0.4-0.6 unit/kg/day
  • Obese may require 0.8-1.2 units/kg/day

Pediatric dosage

  • Children younger than 12 years of age: Safety and efficacy not established
  • Children 12 years of age or older: 0.5-1 unit/kg/day SC; use adult dosing; usual daily maintenance range in adolescents is less than or equal to 1.2 units/kg/day during growth spurts

Type 2 Diabetes Mellitus

  • Suggested guidelines for beginning dose: 0.2 unit/kg/day


  • Give two-thirds of daily insulin SC
  • The ratio of regular insulin to NPH insulin is 1:2


  • Give one-third of daily insulin SC
  • The ratio of regular insulin to NPH insulin is 1:1

Dosage Considerations – Should be Given as Follows: 

  • See “Dosages”.

What Other Drugs Interact with Insulin NPH?

If your medical doctor is using this medicine to treat your pain, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first

  • Insulin NPH has severe interactions with the following drug:
  • Insulin NPH has serious interactions with the following drugs:
  • Insulin NPH has moderate interactions with at least 124 other drugs.
  • Insulin NPH has minor interactions with at least 77 other drugs.

This information does not contain all possible interactions or adverse effects. Visit the RxList Drug Interaction Checker for any drug interactions. Therefore, before using this drug, tell your doctor or pharmacist about all the drugs you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist. Check with your physician if you have health questions or concerns.

What are warnings and precautions for Insulin NPH?


  • Hypoglycemia
  • Documented hypersensitivity reactions to products or excipients

Effects of drug abuse

  • None

Short-Term Effects

  • See “What Are Side Effects Associated with Using Insulin NPH?”

Long-Term Effects

  • See “What Are Side Effects Associated with Using Insulin NPH?”


  • Never share a pen between patients even if the needle is changed
  • Intermediate-acting insulin; do not use for circumstances that require a rapid-acting insulin
  • Caution with decreased insulin requirements: Diarrhea, nausea/vomiting, malabsorption, hypothyroidism, renal impairment, hepatic impairment
  • Hypokalemia may occur
  • Not for IV or IM administration
  • Use with caution in renal and hepatic impairment (dosage requirements may be reduced)
  • Caution with increased insulin requirements: Fever, hyperthyroidism, trauma, infection, surgery
  • Thiazolidinediones are peroxisome proliferator-activated receptor (PPAR)-gamma agonists and can cause dose-related fluid retention, particularly when used in combination with insulin; fluid retention may lead to or exacerbate heart failure; monitor for signs and symptoms of heart failure, treat accordingly, and consider discontinuing thiazolidinediones
  • When hyper-or hypoglycemia occurs, carry out changes in insulin regimen under close medical supervision; increase frequency of blood glucose monitoring

Hyperglycemia or hypoglycemia with changes in insulin regimen

  • Hypoglycemia may be life-threatening; increase the frequency of blood glucose monitoring with changes to insulin dosage, co-administered glucose-lowering medications, meal pattern, and physical activity; in patients with renal or hepatic impairment; and patients with hypoglycemia unawareness
  • Changes in insulin, insulin strength, manufacturer, type, or method of administration may affect glycemic control and predispose to hypoglycemia or hyperglycemia
  • Changes should be made cautiously and only under close medical supervision and the frequency of blood glucose monitoring should be increased
  • Repeated insulin injections into areas of lipodystrophy or localized cutaneous amyloidosis are reported to result in hyperglycemia; a sudden change in the injection site (to the unaffected area) has been reported to result in hypoglycemia
  • Make any changes to a patient’s insulin regimen under close medical supervision with increased frequency of blood glucose monitoring
  • Advise patients who have repeatedly injected into areas of lipodystrophy or localized cutaneous amyloidosis to change injection site to unaffected areas and closely monitor for hypoglycemia
  • For patients with type 2 diabetes, dosage adjustments in concomitant oral antidiabetic treatment may be needed

Pregnancy and Lactation

  • Available data from published studies over decades have not established an association between human insulin use during pregnancy and major birth defects, miscarriage, or adverse maternal or fetal Outcomes; there are risks to mother and fetus associated with poorly controlled diabetes in pregnancy; animal reproduction studies were not performed
  • Poorly controlled diabetes in pregnancy increases the maternal risk for diabetic ketoacidosis, preeclampsia, spontaneous abortions, preterm delivery, stillbirth, and delivery complications; poorly controlled diabetes increases the fetal risk for major birth defects, stillbirth, and macrosomia-related morbidity
  • Available data from published literature suggests that exogenous human insulin products are transferred into human milk; there are no adverse reactions reported in breastfed infants in the literature; there are no data on the effects of exogenous human insulin products, on milk production; the developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for therapy, and any potential adverse effects on the breastfed infant from the drug, or underlying maternal condition.
Medscape. Insulin NPH.

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