Merck Manual

Please confirm that you are a health care professional

honeypot link
  • Ready Reference Guides
    In the US, most laboratory test results are reported in what are termed conventional units; the rest of the world reports results in Système International d’Unités (SI) or international units (IU). The unit basis for SI is updated periodically by a panel.

  • Normal Laboratory Values
    Reference values (intervals) for blood, urine, CSF, stool, and other fluids (eg, gastric acid) and commonly used panels are included. (Note: The reference values provided in these tables should be used as guidelines only.) Reference values vary based on several factors, including the demographics of the healthy population from which specimens were obtained and the specific methods and/or instruments used to assay these specimens. Laboratories that are accredited by the College of American Pathologists (CAP) are required to establish and/or validate their own reference values at least annually. Thus, any given result should be interpreted based on the reference value of the laboratory in which the test was done; the laboratory typically provides these values with the test result.