Common Prescription Abbreviations · What They Are, What They Mean, and More

Ante cibum (AC) is a Latin phrase that translates to “before meals” and it’s often written on medical prescriptions. For example, a prescription may be written as “Take 1 tablet daily AC.” It’s important to counsel patients on these directions as some medications are meant to be taken on an empty stomach since the absorption of certain medications may be impaired by food. Examples include thyroid medications, such as levothyroxine, and bisphosphates, like alendronate, which are used to treat osteopenia and/or osteoporosis.

Post cibum (PC) is a Latin phrase that translates to “after meals,” and similarly to “AC,” it’s often written on prescription labels. One example is, “Take 1 tablet daily PC.” It’s a specific medical abbreviation that instructs patients to take their medications after meals. Some medications, such as HIV antivirals (e.g., tenofovor disoproxil, elvitegravir, atazanavir), require a large meal for maximal absorption. In the absence of solid food, these medications may not be properly absorbed. In other instances, other medications may irritate the stomach lining, such as non-steroidal anti-inflammatory drugs (NSAIDs), and therefore, taking with food may help with gastrointestinal adverse effects.

Hora somni (HS) is a Latin phrase that translates to “take at bedtime.” For example, “Take 1 tablet HS” instructs patients to take their medications in the evening. Some medications may cause drowsiness or sedation and are therefore recommended to be taken at night (e.g., melatonin, zolpidem). Whereas other medications such as anti-cholesterol medications, like simvastatin and lovastatin, are recommended to be taken at bedtime since cholesterol production peaks at night.

Quaque die (QD) is a Latin phrase that translates to “once daily.” Prescriptions written as “Take 1 tablet QD” are written as medications to be taken once a day. For example, many anti-hypertensives (e.g., losartan), statins (e.g., atorvastatin) and vitamins (e.g., Vitamins A, D, E, K) are taken daily.

Bis in die (BID) is a Latin phrase that translates to “two times a day.” Prescriptions written as “Take 1 tablet BID” instruct patients to take the medication two times a day. Commonly, people will take one tablet in the morning (8 AM) and one in the evening (8 PM). For example, diabetes medications (e.g., metformin) and beta blockers (e.g., carvedilol) are often taken twice daily.

Ter in die (TID) is a Latin phrase that translates to “three times a day.” Prescriptions written as “Take 1 tablet TID” instruct patients to take the medication three times a day. An example schedule may involve taking one tablet each at 8AM, 2PM, and 8PM. For example, some anticonvulsants like gabapentin may be taken three times a day.

Quater in die (TID) is a Latin phrase that translates to “four times a day.” Prescriptions can be written as “Take 1 tablet QID” and instruct patients to take the medication four times a day. Some medications have shorter half-lives and therefore require more frequent dosing to maintain a steady state concentration of the active ingredient in the body, therefore a more frequent dosing schedule can be used. Some examples include antibiotics, such as amoxicillin, and opioids, like morphine.

Pro re nata (PRN) is a Latin phrase that translates to “as needed.” For example, a prescription may be written as “Take 1 tablet for headache PRN.” Medications aimed at supportive care (e.g., nausea, vomiting, pain) measures are often written PRN. It allows the patient to take the medication when they experience symptoms. For example, bowel regimens (e.g., polyethylene glycol) or antipyretics (e.g., acetaminophen) may be taken as needed.

Nil per os (NPO) is a Latin phrase that translates to “nothing by mouth.” NPO instructions such as “NPO at midnight” means that the patient should not drink or eat anything by mouth starting at midnight. This is especially important when hospitalized patients are scheduled for surgery or a procedure the following day. This keeps the stomach empty, minimizes aspiration of food/liquid during the operation, and prevents serious complications. For example, prior to certain procedures (e.g., endoscopy or biopsy) or imaging (e.g., abdominal ultrasound), patients may be instructed not to eat or drink food or liquids after midnight.

Prescription abbreviations are often used when healthcare providers write and send prescriptions to the pharmacy. The list of abbreviations are derived from Latin words and include AC, PC, HS, QD, BID, TID, QID, PRN, and NPO. While these were commonly used in the past, it’s highly encouraged to spell out the instructions, rather than using abbreviations, as they have led to medication errors. For example, QD may sometimes be confused with QID, resulting in patient harm.