Deciphering Dosage Timing With 4-Times-a-Day or Every 6 Hours (2024)

QID and Q6H are both medical abbreviations used on prescription medications. QID medications should be taken four times a day, while Q6H should be taken every six hours. While this may seem redundant, it's not. There's a key difference.

With QID medications, you need to space out your doses, but not by a specific number of hours. You can take your last dose before going to bed instead of waking up at night to take it.

Medications labeled Q6H need to be taken following a specific schedule. You may need to wake up at night to take a dosage to make sure you're spacing each dose six hours apart.

This article explains the medical abbreviations QID and Q6H and covers other common medical terms used to describe how and when to take your medicine.

Deciphering Dosage Timing With 4-Times-a-Day or Every 6 Hours (1)

Medical Abbreviation QID

The medical abbreviation QID means four times a day. It may be written as QID, qid, or q.i.d. It is Latin for quater in die, which translates to "four times per day."

You only need to take QID medication when you're awake. Your prescription may come with the note "QID while awake" or something similar to clarify that this is the case.

The following times of day are optimal for taking QID medication, and the time between doses doesn't have to be exact:

  • In the morning
  • Around noon
  • In the evening
  • At night before bed

Difference Between Drug Dose and Dosage

Medical Abbreviation Q6H

Whether written as Q6H, q6h, or q.6.h., this medical abbreviation stands for the Latin phrase quaque 6 hora, or "every six hours." Q6H medications are categorized as around-the-clock (ATC) medications. ATC medications need to be taken at set intervals so the drug levels in your blood stay consistent and high enough.

ATC medications include drugs for heart disease and high blood pressure as well as blood thinners (drugs that keep your blood from clotting). Severe pain is also often managed with ATC dosing. Pain tends to come back quickly once the dose wears off. Taking the right dose at set intervals may help keep your pain from spiking.

If you're prescription says Q6H, you can take your doses at the following times or at any other time of day as long as you keep a six-hour regimen:

  • First dose at 6:00 a.m.
  • Second dose at 12:00 p.m.
  • Third dose at 6:00 p.m.
  • Fourth dose at 12:00 a.m.

Common Medical Abbreviations on Prescriptions

You may see these abbreviations on your prescription, and your pharmacy should give you written instructions explaining them.

Abbrev.LatinMeaningOther Info
POper osOrally (by mouth)
BIDbis in dieTwice a day
TIDter in dieThree times a day
QIDquater in dieFour times a day
Q4Hquaque 4 horaEvery four hours
Q6Hquaque 6 horaEvery six hours
Q8Hquaque 8 horaEvery eight hours
Q12Hquaque 12 hora
PRNpro re nataAs neededUsually for mild or intermittent symptoms
AC or QACante cibum or quaque ante cibumBefore a mealMay be followed with a set amount of time before eating, such as one hour
PCpost cibumAfter a meal
IMIntramuscular (into the muscle)For injections only
SubQ, SQ, or SCSubcutaneous (under the skin)For injections only
IVIntravenous (in a vein)Given via an IV line or port
GTTguttaDropsFor eye drops, ear drops, etc.
ODoculus dexterRight eyeFor drops or ointments
OSoculus sinisterLeft eyeFor drops or ointments
OUoculus uterqueBoth eyesFor drops or ointments

Some abbreviations, like QD (once a day), QOD (every other day), and others, can be easily confused with one another and are no longer used. These terms must be written out because they can contribute to medication errors.

Preventing Medication Errors

Medication errors can and do happen. They often cause side effects, which may require an emergency room visit or hospitalization. Some errors lead to death, including those involving opioid medications. It's estimated that half of these errors are preventable.

Help prevent medication errors by being your own advocate:

  • Make sure the prescription you get is the prescription your provider intended: Check the instructions on the medication you pick up to make sure that they match the instructions from your healthcare.
  • Request plain language: You can always ask your provider to write out your prescription instructions in terms you can clearly follow.
  • Ask for a prescription to be digitally sent to your pharmacy: This may reduce the likelihood of handwriting being misinterpreted.

7 Questions to Ask Before Taking a Prescription


Healthcare providers often use shorthand terms when prescribing a drug. They may use abbreviations on prescriptions, such as QID and Q6H. These and other forms of medical shorthand are well known in the healthcare setting. But using them is by no means a required practice.

Be sure your provider or pharmacist clearly explains how and when to take your medicine. Ask them to clarify what you do not understand or would like to know about this drug. This can help prevent medication errors.

4 Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

  1. National Institutes of Health, U.S. National Library of Medicine. Warfarin.

  2. Scarborough BM, Smith CB. Optimal pain management for patients with cancer in the modern era. CA Cancer J Clin. 2018;68(3):182-196. doi:10.3322/caac.21453

  3. Lockwood W. Medical errors prevention and safety.

  4. Agency for Healthcare Research and Quality, Patient Safety Network. Medication errors and adverse drug events.

Additional Reading

By Michael Bihari, MD
Michael Bihari, MD, is a board-certified pediatrician, health educator, and medical writer, and president emeritus of the Community Health Center of Cape Cod.

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