insulin NPH (OTC)

Brand and Other Names:Humulin N, Novolin N
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Dosing & Uses


Dosage Forms & Strengths

injectable suspension

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

Type 1 Diabetes Mellitus

Suggested guidelines for beginning dose

  • Usual daily maintenance range is 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

Type 2 Diabetes Mellitus

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


  • Give two thirds of daily insulin SC
  • Ratio of regular insulin to NPH insulin 1:2


  • Give one third of daily insulin SC
  • Ratio of regular insulin to NPH insulin 1:1

Dosing Considerations

Dosage of human insulin, which is always expressed in USP units, must be based on the results of blood and urine glucose tests and must be carefully individualized to optimal effect

Dose adjustments should be based on regular blood glucose testing

Adjust to achieve appropriate glucose control

Blood sugar patterns (>3 days)

  • Look for consistent pattern in blood sugars for >3 days
  • For the same time each day: Compare blood glucose level
  • For each time of day: Calculate blood glucose range
  • Calculate median blood glucose
  • Consider eating and activity patterns during day

Blood glucose adjustments

  • Adjust only 1 insulin dose at a time
  • Correct hypoglycemia first
  • Correct highest blood sugars next
  • If all blood sugars are high (within 2.75 mmol/L [50 mg/dL]): Correct morning fasting blood glucose first
  • Change insulin doses in small increments: Type 1 diabetes (1-2 unit change); type 2 diabetes (2-3 unit change)

Sliding scales

  • Many sliding scales exist to determine exact insulin dose based on frequent blood glucose monitoring
  • Commonly written for q4hr blood glucose test
  • Sliding scale coverage usually begins after blood glucose >11 mmol/L (200 mg/dL)
  • If coverage is needed q4hr x 24 hr, then base insulin dose is adjusted first; sliding scale doses may be adjusted upwards as well


Administer within 15 minutes before a meal or immediately after a meal

Dosage Forms & Strengths

injectable suspension

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

Type 1 Diabetes Mellitus

<12 years: Safety and efficacy not established

>12 years: Suggested dose is 0.5-1 unit/kg/day SC; use adult dosing; usual daily maintenance range in adolescents is ≤1.2 units/kg/day during growth spurts

Dosing considerations

  • Dosage of human insulin, which is always expressed in USP units, must be based on the results of blood and urine glucose tests and must be carefully individualized to optimal effect


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            Adverse Effects

            Frequency Not Defined




            Local allergic reaction


            Muscle weakness








            Numbness of mouth

            Postmarketing Reports

            Localized cutaneous amyloidosis





            Documented hypersensitivity reactions to product or excipients


            Never share pen between patients even if needle is changed

            Intermediate-acting insulin; do not use for circumstances that require 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 frequency of blood glucose monitoring with changes to: insulin dosage, co-administered glucose lowering medications, meal pattern, physical activity; in patients with renal or hepatic impairment; and in 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 frequency of blood glucose monitoring should be increased
            • Repeated insulin injections into areas of lipodystrophy or localized cutaneous amyloidosis reported to result in hyperglycemia; a sudden change in the injection site (to 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 & Lactation


            Available data from published studies over decades have not established association with 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 maternal risk for diabetic ketoacidosis, preeclampsia, spontaneous abortions, preterm delivery, stillbirth, and delivery complications; poorly controlled diabetes increases 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 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 breastfed infant from drug, or from underlying maternal condition

            Pregnancy Categories

            A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

            B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

            C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

            D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

            X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

            NA: Information not available.



            Mechanism of Action

            Regulates glucose metabolism

            Insulin and its analogues lower blood glucose by stimulating peripheral glucose uptake, especially by skeletal muscle and fat, and by inhibiting hepatic glucose production; insulin inhibits lipolysis and proteolysis and enhances protein synthesis; targets include skeletal muscle, liver, and adipose tissue

            Insulin NPH and insulin regular is a combination insulin product with intermediate action that has more rapid onset than that of insulin NPH alone


            Bioavailability (IM, SC, IP): Well absorbed

            Onset: 1-1.5 hr (a combination insulin product, insulin NPH and insulin regular, also has intermediate action, but it has a more rapid onset than does insulin NPH alone); 4-12 hr peak effect

            Duration: 14-24 hr

            Peak plasma time: 6-10 hr


            Protein bound: 5% (not bound to serum binding protein, but present as a monomer in plasma)

            Vd: 0.15 L/kg


            Excretion: Urine



            Medscape prescription drug monographs are based on FDA-approved labeling information, unless otherwise noted, combined with additional data derived from primary medical literature.