insulin in serum

Reference interval

• free insulin (see Procedure:)
  • adult: < 17 uIU/mL (< 118 pmol/L)
  • infants & prepubertal children: < 13 uIU/mL (< 90 pmol/L)

Increases

• pharmaceutical agents
  • in vivo
    • acetohexamide, albuterol, amino acids, calcium gluconate (newborn), chlorpropamide, cyproheptadine (non-diabetics), danazol, fructose, glucagon, glucose, growth hormone, levodopa, medroxyprogesterone, niacin, oral contraceptives, pancreozymin (IV), phentolamine (IV), prednisolone, quinidine, secretin (IV), spironolactone, sucrose, terbutaline, tolazamide, tolbutamide
• clinical disorders
  • insulinoma
  • diabetes mellitus, type 2
  • liver disease
  • acromegaly
  • Cushing's syndrome
  • myotonic dystrophy
  • familial fructose & galactose intolerance
  • obesity
  • surreptitious use of insulin or sulfonylureas

Decreases

• pharmaceutical agents
  • in vivo
    • beta-blockers, asparaginase, bezafibrate, calcitonin, chlorpropamide, cimetidine, clofibrate, diazoxide, doxazosin, ethacrynic acid, ethanol, ether, furosemide, metformin, nifedipine, phenformin, phenobarbital, phenytoin, thiazides, tolbutamide (some patients)
  • chemical interferences
    • hemolysis, heparin (some assays)
• clinical disorders
  • diabetes mellitus, type 1
  • hypopituitarism

Methods

• RIA
• immunometric assay (2-site)
  • no cross reaction with pro-insulin

Specimen

• serum
• separate from cells as soon as possible
• freeze immediately
• store frozen

Procedure

• free (bioactive) insulin is measured after polyethylene glycol (PEG) precipitation of anti-insulin antibodies & their bound insulin
• total insulin may be measured by acidification of the sample to dissociate insulin from endogenous antibodies before treatment with PEG
• if insulin antibodies are not present, free & immunoreactive insulin assays are the same
• simultaneous measurement of C-peptide is suggested to evaluate hypoglycemia due to surreptitious use of insulin

Notes

• little clinical value except for evaluation of fasting hypoglycemia

More general terms

• special chemistry test

Additional terms

• C-peptide in serum

Component of

• glucose/insulin in serum/plasma
• endocrinology 7 analyte panel
• insulin-induced C-peptide suppression panel
• proinsulin/insulin in serum/plasma

Patient information

insulin in serum patient information