What does bid mean on a prescription?

Twice a day. It comes from the Latin bis in die. It tells you how many doses to take in a day, not the exact times, so ask your pharmacist if the times matter for your medicine.

Is bid the same as every 12 hours?

No. bid means twice a day, and q12h means every 12 hours. Every 12 hours keeps an even gap around the clock; twice a day doesn't say how far apart the doses are.

As needed, from the Latin pro re nata. Next to a time, as in q6h prn, it reads every 6 hours as needed.

Every night at bedtime, from the Latin quaque hora somni. hs on its own also means at bedtime.

Why does my label say daily instead of qd?

qd has been misread as qid, four times a day. The Institute for Safe Medication Practices lists it as error-prone, The Joint Commission has it on its Do Not Use list, and both ask for daily to be written out.

By mouth, from the Latin per os. The long form per os is no longer recommended, because os has been misread as left eye.

Prescription glossary

Prescription abbreviations: what bid, tid, qid and prn mean

Prescription abbreviations are short forms, most of them from Latin, for how often and how to take a medicine. bid means twice a day, tid three times a day, qid four times a day and prn as needed. q8h means every 8 hours, qhs every night at bedtime, ac before meals and po by mouth. The full list is below.

Prescription abbreviations and what they mean

Abbreviation	Means	From the Latin
How many times a day
bid	Twice a daybis in die	bis in die
tid	Three times a dayter in die	ter in die
qid	Four times a dayquater in die	quater in die
daily	Once a day. Older labels say qd, which is no longer recommended (see below).quaque die (qd)	quaque die (qd)
Every few hours
q4h	Every 4 hoursquaque quarta hora	quaque quarta hora
q6h	Every 6 hoursquaque sexta hora	quaque sexta hora
q8h	Every 8 hoursquaque octava hora	quaque octava hora
q12h	Every 12 hours
When to take it
qam	Every morningquaque ante meridiem	quaque ante meridiem
hs, qhs	At bedtime. qhs is every night at bedtime.quaque hora somni	quaque hora somni
ac	Before mealsante cibum	ante cibum
pc	After mealspost cibum	post cibum
prn	As neededpro re nata	pro re nata
stat	Right awaystatim	statim
How to take it
po	By mouthper os	per os
sl	Under the tongue

Sources: ISMP Canada, reading your prescription; ISMP List of Error-Prone Abbreviations (daily, qhs); Wikipedia (Latin, q6h, q8h)

This page explains what the abbreviations mean. It isn't medical advice: follow your prescriber's instructions, and ask your pharmacist if anything on your label isn't clear.

Doser, a medication reminder for iPhone, turns bid, tid or q8h into alarms at the times you set.

See how Doser works

BID vs every 12 hours: are they the same?

Not quite. bid counts doses: two in a day. It doesn't say how far apart they are. q12h fixes the gap instead: a dose, then the next one 12 hours later, around the clock.

The same goes for tid and q8h. Three times a day is a count; every 8 hours is a clock. So a twice-a-day medicine can be taken at whatever two times your prescriber or pharmacist gives you, while every 12 hours keeps to the clock.

For some medicines the gap matters and for others it doesn't, and only your pharmacist or prescriber can tell you which yours is. If your label says bid or tid and you're not sure what times to use, ask them.

Meanings: ISMP Canada

Abbreviations that are no longer recommended

The Institute for Safe Medication Practices (ISMP) collects abbreviations that have been misread and led to medication errors, and asks prescribers and pharmacies to write the words out instead. You may still see them on older labels. qd and qod are also on The Joint Commission's official Do Not Use list.

qd
Was meant as:
Every day
Has been misread as:
qid, four times a day
Written today as:
daily
qod
Was meant as:
Every other day
Has been misread as:
qd (daily) or qid (four times a day)
Written today as:
every other day
q1d
Was meant as:
Daily
Has been misread as:
qid, four times a day
Written today as:
daily
TIW, BIW
Was meant as:
3 times a week, 2 times a week
Has been misread as:
3 times a day or twice a week; 2 times a day
Written today as:
3 times weekly, 2 times weekly
UD
Was meant as:
As directed
Has been misread as:
Unit dose
Written today as:
as directed
per os
Was meant as:
By mouth
Has been misread as:
The "os" as left eye
Written today as:
PO, by mouth or orally

If your label has one of these, it still means what it was meant to. If anything looks off, say qid where you expected once a day, check with your pharmacist before your next dose.

ISMP List of Error-Prone Abbreviations, 2024

How to read a line on your prescription

A prescription line usually goes: how much, how, how often, and sometimes when. Read it left to right with the table above. Here are a few common lines in plain words (tab is tablet, cap is capsule).

1 tab po bidTake 1 tablet by mouth twice a day.
2 caps po tid pcTake 2 capsules by mouth three times a day, after meals.
1 tab po qhsTake 1 tablet by mouth every night at bedtime.
1 tab po q8hTake 1 tablet by mouth every 8 hours.
1 tab po q6h prnTake 1 tablet by mouth every 6 hours as needed.

Once you know the count, ask your pharmacist what times suit your medicine, and set your reminders to those.

How long will your pills last? Work out your refill date

Turn the label into reminders

Knowing what bid means is the easy part. Taking it twice a day, every day, is where doses slip. Doser, a medication reminder for iPhone, turns the schedule on your label into alarms at the times you set.

Once, twice or several times a day, every few hours, on certain weekdays or every few days.
Every dose is a real alarm that rings through silent mode and Focus.
One tap logs a dose, or log it with Siri or the Action button.

For iPhone. An Android version is on the way.

See how Doser works

Doser's Today screen asking whether the afternoon dose was taken, with the morning doses already done

Questions people ask

What does bid mean on a prescription?: Twice a day. It comes from the Latin bis in die. It tells you how many doses to take in a day, not the exact times, so ask your pharmacist if the times matter for your medicine.
Is bid the same as every 12 hours?: No. bid means twice a day, and q12h means every 12 hours. Every 12 hours keeps an even gap around the clock; twice a day doesn't say how far apart the doses are.
What does prn mean?: As needed, from the Latin pro re nata. Next to a time, as in q6h prn, it reads every 6 hours as needed.
What does qhs mean?: Every night at bedtime, from the Latin quaque hora somni. hs on its own also means at bedtime.
Why does my label say daily instead of qd?: qd has been misread as qid, four times a day. The Institute for Safe Medication Practices lists it as error-prone, The Joint Commission has it on its Do Not Use list, and both ask for daily to be written out.
What does po mean?: By mouth, from the Latin per os. The long form per os is no longer recommended, because os has been misread as left eye.

You know what the label says. Doser remembers it.

Doser rings when a dose is due, even on silent, and keeps ringing until you answer. For iPhone.

Updated October 2026 · By Tupungato Studios