4 Times-a-Day (QID) or Every 6 Hours (Q6H) Prescription

Deciphering Dosage Instructions and Timing

Pharmacist talking to customer
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If your doctor has prescribed a medication using terminology such as QID or Q6H, what does that mean? If a medication is prescribed every 4 to 6 hours, do you need to awaken at night to take it?  How can you interpret all of the other medical lingo describing your medication? Let's translate what these terms mean so that you can take your medication the way that your physician—though speaking in what appears to be a foreign language—intended.

Medication Timing on a Physician's Prescription

Many people have questions about timing when they get a prescription, look at orders on a discharge sheet, or remember instructions given in the office or hospital. You may be googling one of these terms hoping that you don't need to call your physician to clarify her instructions.

While we can't be certain the intent of your physician, nor know what was said in the office, we can provide you with a definition of some of these terms that can hopefully help you take your medication the way it's intended. Let's start with one important concept: the number of doses to be taken daily versus how often to take your medication.

Differences Between QID (Take 4 Times Daily) and q6H (Take Every 6 Hours)

One distinction in medication instructions is when a medication is prescribed at a specific time interval, or instead, is written as a number of doses to be taken daily. An example would be a prescription that is prescribed QID (translated to mean take the medication 4 times a day,) and q6h, which would mean to take the medication every six hours. What is the difference?

First, we have to clarify that what your doctor wrote may not represent exactly what she was thinking. If in doubt, always ask. When a medication is prescribed QID (4 times a day) it is most often assumed that the medication will be taken 4 times a day spread out over waking hours. In contrast, a prescription prescribed q6h (every 6 hours) is usually designed to be taken every 6 hours, even if you have to set an alarm and wake up to make sure you follow this schedule.

When can drugs be taken only during waking hours and when is a set schedule, instead, important?

Around the clock medications—those which you need to take at a regular time interval, say every 6 hours—may be needed to keep the levels of the drug in your bloodstream above a certain number. If the amount of the drug in your bloodstream at any one time during a 24 hour day is important, taking a drug at a set interval is recommended. A regular interval is often recommended with a high blood pressure medication, a heart disease medication, or something such as a blood thinner. To understand this you may want to think about how the medication works. With a blood thinner, for instance, you want to make sure your levels are relatively constant over time. With a QID schedule, you'd be apt to have leveled a bit higher than normal at some times and lower than normal at others.

In contrast, if you are using a medication for mild pain or itching, using it during waking hours (for example q6h) may be the best option if you don't need the medication in your system while you are asleep. Some physicians clarify this on a prescription, for example writing either QID or q6h (or other timing) while awake.

ATC is an acronym which refers to around the clock medications. This is usually used for medications such as heart medications, but may be used for pain medications as well, especially when getting behind on the medications may cause a rebound of pain symptoms. With severe pain, and especially with pain medications used at the end of life, pain medications will be recommended ATC instead of PRN (as needed) to maintain better pain relief.

The severity of the need for the medication may also determine the timing. For an infection such as a strep throat, a medication may be prescribed 4 times daily while awake. For a life-threatening infection, in contrast, it's important to take a medication at set intervals (for example, every 4 hours) to make sure your blood levels of the drug are never below therapeutic levels.

Other Notations Found on Prescriptions

Our examples of QID and q6h above are only one example of how timing is depicted on a prescription. Here are the translations of some of the other notations that you may read or hear from your doctor:

  • PO means orally
  • QD means once a day
  • BID means twice a day
  • TID means three times a day
  • QID means four times a day
  • QHS means before bed
  • Q4H means every 4 hours
  • Q6H means every 6 hours
  • Q8H means every 8 hours
  • QOD means every other day
  • PRN means as needed - PRN medications are usually those that are only needed for minor symptoms, such as pain, nausea, or itching
  • a.c. means before a meal (it may also be written q.a.c.) - The prescription may also include how long before a meal the medication needs to be taken, for example, one hour before eating (these are usually medications which need to be taken on an empty stomach for proper absorption so this description is important)
  • p.c. means after a meal - Some medications are absorbed better with a full stomach, though sometimes medications are recommended after a meal to decrease stomach upset
  • IM means intramuscularly (injection) - Intramuscularly means the injection is given into a muscle
  • Subq means subcutaneous (injection) - Subcutaneous means the injection is given just under the surface of the skin, like a tuberculosis test
  • IV means intravenous (injection) - Intravenous injections are usually given through an intravenous line or a Port
  • q.t.t. means drops
  • OD means in the right eye (think eye drops)
  • OS means in the left eye (think eye drops)
  • OU means in both eyes (think eye drops)

Other Notations on Mediation Timing

Additionally, you may see a symbol on your script that looks like a "T" with a dot at the top of it. This abbreviation means one pill. There may be one to 4 T's with dots at the top of them signifying one to 4 pills.

Obviously, you may not see all of these abbreviations in one script. For example, OD, OS, and OU are used only for drops and not for pills.

Please remember that in addition to your physician, your pharmacist is an excellent resource when it comes to figuring out how your drugs work, their adverse effects, or how your drugs should be taken. Pharmacists are knowledgeable and trained to answer all your questions. (Like physicians, pharmacists go to graduate school and many complete residencies.) Many people pass on asking their pharmacists questions, which is unfortunate because a pharmacist can be a very valuable resource. Thus, the next time you're at the pharmacy and have a question please feel free to ask your pharmacist.

More Information About Your Prescription Medications

The timing of doses isn't the only question people may have when it comes to deciphering prescriptions or oral communication from your doctor. You should learn more about prescription abbreviations and how to read your doctors prescription with regard to other concerns, such as the number of refills allowed, and whether you are receiving a brand name or generic drug.

Finally, you've likely heard the news that medical errors are a significant cause of death in the United States. Fortunately, most of these errors are preventable when patients are active advocates for their health and ask plenty of questions. You should ask any of these 15 questions you should ask your doctor about any medication you are prescribed. You may also want to make sure you are familiar with how you can avoid medication errors.

And to ensure your safety, make sure you do these things every time you get a medication filled.

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