Which of the following abbreviations in a prescription indicates a medication is to be taken every hour?

t.i.d. (on prescription): Seen on a prescription, t.i.d. means three times a day. It is an abbreviation for "ter in die" which in Latin means three times a day. The abbreviation t.i.d. is sometimes written without a period either in lower-case letters as "tid" or in capital letters as "TID". 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. (or bid or BID) is two times a day ; b.i.d. stands for "bis in die" (in Latin, twice 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).
• q_h: If a medicine is to be taken every so-many hours, it is written "q_h"; the "q" standing for "quaque" and the "h" indicating the number of hours. So, for example, "2 caps q4h" means "Take 2 capsules every 4 hours."

QID and Q6H are abbreviations used by medical professionals to indicate how many times a day you should take a medication and at what intervals. QID means a dose should be taken four times daily, while Q6H means that dose should be taken every six hours.

These abbreviations are usually written on the prescription from your healthcare provider so that the pharmacy can dispense your medication with the proper instructions. You will likely see QID and Q6H translated into plain English on the prescription's packaging.

Note: While Q6H is common, a healthcare provider can replace the six with whatever number is appropriate for the prescription.

This article covers common medical terms used to describe how and when to take your medicine.

Meaning of QID

This abbreviation may be written as QID, qid, or q.i.d. Its literal meaning is the Latin phrase quater in die, which translates to "four times per day."

Certain doses of your medicine only need to be taken while you're awake. Your symptoms may be mild enough that you don't need a dose to hold you through the night.

In this case, your healthcare provider may prescribe the drug with the note "QID while awake" or something similar to clarify that you only need to take the drug during wakeful hours.

How to Follow This Dosing Schedule

QID indicates that a medication needs to be taken a total of four times throughout the day. It does not indicate the schedule you need to follow to achieve that.

In other words, you can space out your doses throughout the day, but the time between them doesn't have to be exact. For example, you might take a dose a breakfast, lunch, and dinner, then right before you head to bed.

Meaning of Q6H

In Latin, Q6H (q6h, q.6h.) is quaque 6 hora, or "every six hours."

If your illness course is more severe or spreading out doses places your health at great risk, around-the-clock (ATC) doses may be needed to make sure the drug levels in your blood stay consistent and high enough. Q6H is one example of ATC dosing.

Certain drugs work best when used at set intervals. Examples include drugs for heart disease and high blood pressure. The level of blood thinners (drugs that keep your blood from clotting) also need to be kept consistent.

If you only take these medications during wakeful hours, your blood level will likely rise and fall instead of staying at a more even level.

Severe pain is often better managed with ATC dosing, as well. That's because 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.

How to Follow This Dosing Schedule

When your healthcare provider is this specific, it means you need to take your doses six hours apart, around the clock.

If that means that your next dose should be taken while you are sleeping, you will need to wake up to take it.

If another interval is indicated (e.g., Q8H, Q12H), adjust your timing accordingly.

More Prescription Abbreviations

Your healthcare provider may put a variety of other abbreviations on your prescription to inform your pharmacist about how they want you to take a medication.

Here too, the meaning of these abbreviations should be clearly written out in the instructions provided by your pharmacy.

The Joint Commission on Accreditation of Healthcare Organizations in 2003 banned the use of QD (once a day), QOD (every other day), and seven other abbreviations, saying they contributed to medication errors. Those terms must now be written out.

Preventing Medication Errors

Medication errors are a significant cause of death in the United States. The good news is most of these errors are preventable.

Things you can do to advocate for yourself include:

• 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 that your healthcare provider explained to you.
• Request plain language: If you aren't confident you'll remember what your provider said about how you should take your medication, don't be afraid to ask them to write out your prescription in terms you can clearly follow—even if they believe a pharmacist will understand medical shorthand.
  
• Ask for a prescription to be digitally sent to your pharmacy: This may reduce the likelihood that something your prescriber writes by hand is misinterpreted.

Summary

Healthcare providers often use shorthand terms when they prescribe 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 explain 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.

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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