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Definition of q_h (on prescription)

  • Medical Author:
    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

q_h (on prescription): If a medicine is to be taken every so- many hours, it is written "q_h"; the "q" standing for the Latin word for once "quaque" and the "h" indicating the number of hours. So, for example, "2 caps q4h" means "Take 2 capsules every 4 hours." However it is written, it is one of a number of hallowed abbreviations of Latin terms that have been traditionally used in prescriptions to specify the frequency with which medicines should be taken.

Other examples include:

  • q.d. (qd or QD) is once a day; q.d. stands for "quaque die" (which means, in Latin, once a day).
  • b.i.d. (bid or BID) is twice a day; b.i.d. stands for "bis in die" (which means twice a day).
  • t.i.d. (or tid or TID) is three times a day ; t.i.d. stands for "ter in die" (in Latin, 3 times a day).
  • q.i.d. (or qid or QID) is four times a day; q.i.d. stands for "quater in die" (in Latin, 4 times a day).
Reviewed on 9/7/2018

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