The AC medical abbreviation, on a prescription or medication order, means before meals: the dose is taken shortly before eating. Its root is the Latin phrase ante cibum, meaning "before food," and it is written AC, ac or a.c.
AC is a busy pair of letters, though. A nurse charting an IV may write "right AC" for the inner elbow, an orthopedic note may mean the acromioclavicular joint of the shoulder, a respiratory therapist may mean a ventilator mode, and an ultrasound report may mean abdominal circumference. Which one applies depends on where it appears. This page starts with the medication meaning, its partner PC for after meals and the combined ACHS, then sorts out the rest.
At a glance
Stands for
Before meals (on medication orders)Latin origin
Ante cibum, before foodWritten as
AC, ac, a.c.Usual timing
Often about 30 minutes before eating, if the label says soOpposite
PC, after meals (post cibum)Other meanings
Antecubital (inner elbow); acromioclavicular joint; assist control ventilation; abdominal circumferenceWhere you see it
Prescriptions, diabetes orders, IV notes, shoulder and ultrasound reports
What the AC medical abbreviation means on a prescription
On a medication order, AC ties a dose to meals rather than to the clock. Some medicines work best on an empty stomach, and others are meant to act as food arrives, such as certain diabetes medicines or medicines that calm the stomach before eating. In both cases, taking them before the meal is the point.
How long before depends on the medicine. Many labels say about 30 minutes before a meal, some say 15, and some say right before eating. AC alone does not set the number of minutes, so the label or pharmacist fills in that detail.
AC with other frequency words
AC rarely stands alone. It usually rides along with a frequency term, and together they set the schedule.
| As written | Plain meaning |
|---|---|
| daily AC breakfast | Once a day, before breakfast |
| TID AC | Three times a day, before each main meal |
| ACHS | Four checks: three premeal and one at bedtime |
| TID PC | Three times a day, after meals |
Diabetes order set: "Fingerstick glucose ACHS; insulin lispro per scale AC." The nurse checks blood sugar before breakfast, lunch, dinner and at bedtime, and gives the mealtime insulin before each meal based on the reading. This shows the format, not a treatment plan.
Right AC and left AC: the antecubital meaning
In nursing and IV notes, AC most often means antecubital, the soft area on the inside of the elbow where veins sit close to the skin. It is a common spot for blood draws and IV lines.
"20 g IV right AC" means a 20 gauge IV catheter was placed in the right antecubital area. "Blood drawn from L AC" means the left inner elbow. This meaning is easy to spot since it comes with a side, a needle or catheter size, or the word IV, and has nothing to do with meals. See the PIV page for more on peripheral IV notes.
AC joint, ventilator AC and other specialty uses
| Setting | AC means | Sample line |
|---|---|---|
| Orthopedics, sports medicine | Acromioclavicular joint, at the top of the shoulder | Grade II AC separation |
| Respiratory therapy, ICU | Assist control, a ventilator mode | Vent AC, rate 14 |
| Obstetric ultrasound | Abdominal circumference of the fetus | AC measures 50th percentile |
| Hearing tests | Air conduction | AC greater than BC bilaterally |
With so many uses, the surrounding words and the author settle which AC is meant. If a line still seems ambiguous, the writer can clarify.
Is AC an error-prone abbreviation?
AC does not appear among the terms The Joint Commission bans. The main risk is mixing it up with its opposite, PC, since the two look alike in quick handwriting and mean the reverse timing. A medicine meant before food taken after food may work less well, and the reverse can cause stomach upset for some drugs.
Many labels and order systems print before meals and after meals in words to avoid that slip. Students learning AC as a pharmacy abbreviation and nursing abbreviation are often taught to spell out the timing on anything a patient will read. The dosing and timing hub lists the related terms together.
This is general information about a common abbreviation. How long before a meal your own medicine should be taken is best confirmed with your pharmacist.
Frequently asked questions
What does AC mean on a prescription?
Written on a script, AC means before meals, from the Latin ante cibum. The label usually prints before meals and may give a number of minutes.
What is the medical abbreviation for before meals?
The abbreviation is AC, also written ac or a.c. Its opposite is PC, after meals.
What does right AC mean in a nursing note?
Right AC means the right antecubital area, the inner elbow. It usually describes where an IV was placed or blood was drawn.
What does TID AC mean?
TID AC means three times a day, before meals. In practice that is before breakfast, lunch and dinner.
What does ACHS mean?
ACHS combines AC with HS: before meals and also at bedtime. Diabetes care uses it most, to schedule glucose fingersticks.