q8h

q8h is a prescription abbreviation used in medical dosing to indicate that a medication should be administered every eight hours. The term originates from the Latin phrase quaque octo hora, meaning “every eight hours.” In practice, q8h generally results in three doses over a 24-hour period, assuming the first dose is given at time zero and subsequent doses are spaced eight hours apart. The exact times can vary depending on the starting time and patient schedule.

This interval is commonly chosen for drugs where a steady concentration in the bloodstream is desired, such as certain antibiotics or analgesics. When a clinician prescribes q8h, additional instructions may specify considerations related to meals, hydration, or monitoring, and the first dose timing is often tailored to fit the patient’s daily routine to improve adherence. Clinicians may also choose alternative schedules, such as q12h or q6h, if the drug’s pharmacokinetics or patient factors warrant different intervals.

Safety and clarity are important with q8h prescriptions. Some healthcare settings discourage the use of abbreviations due to potential misreading, so spelling out “every eight hours” or providing clear dosing clocks is encouraged to reduce error. Dosing frequency may be adjusted for renal impairment, pediatric patients, or other special populations, and patients should follow the prescriber’s instructions or contact a clinician with questions about missed doses or dosing changes.