Required Elements of a Legal Prescription

A prescription is a written, verbal, or electronic order (1) from a licensed practitioner, (2) to a pharmacist, (3) for a particular medication, (4) for a specific patient, (5) at a particular time. It has three components: a heading, a body, and a closing (Figure 3). These elements identify the prescriber and the patient; inform the pharmacist of the name, strength, and formulation of the drug to be dispensed; and provide instructions to the patient for self-administration of the drug.

Figure 3. Components of a prescription.
components of a prescription

Orders for legend, Schedule III, Schedule IV, and Schedule V drugs may be issued either orally or in writing. Orders for Schedule II drugs must be written. A practitioner may call-in a Schedule II prescription to a pharmacist, but the amount must be limited for the emergency period and the oral order must be followed up by a written order within 72 hours. Prescriptions must always be written legibly, words and numbers spaced out to avoid confusion, and all information verified.


The prescriber’s name, i.e., the licensed practitioner’s address, and phone number validate the prescription, provide contact information, and identify the practitioner’s primary place of business. The patient’s full first and last name are imperative, the middle initial may be helpful. The patient’s gender and age is useful to the pharmacist in determining the appropriateness of the medication and/or the proper dosage to be dispensed.

The date when a prescription was issued or written allows for a determination of the life of the prescription to validate refills. A prescription for legend drugs expires 1 year from the date of issue. A prescription for schedule III, IV, and V drugs expires in 6 months. A prescription for schedule II drugs expires in 7 days. These limitations placed on the life of a prescription are intended to foster ongoing patient supervision and follow-up.


The body of the prescription includes the symbol RX followed by the name of the drug (generic or brand name), which must be written out in full. The strength of a drug’s unit dose is to be written in the metric system, e.g., in grams (g) or milligrams (mg) for solid formulations and in milligram per milliliter (mg/ml) for liquid formulations.25 Under directions for the patient it may be necessary to convert milliliters to a convenient household measurement (Table 5).25

Table 5. Common metric and household measures.25
kilogramkg1 kg1000 g
gramg1 g1000 mg
milligrammg1 mg1/1000 g
poundlb1 kg2.2 lb
graingr1 gr65 mg
literL1 L1000 ml
teaspoontsp1 tsp5 ml
tablespoontbsp1 tbsp15 ml
dropgtt15 gtt1 ml
fluid ouncefl oz1 fl oz30 ml

When writing dosage strength, always use leading zeros, e.g., write 0.5 ml versus .5 ml (which can be mistaken for 5 ml); and avoid trailing zeroes, e.g., write 5 mg versus 5.0 mg (which can be mistaken for 50 mg). When the strength of a unit dose is 1 milligram or more, but less than 1 gram, it should be written in milligrams (e.g., write 200 mg, not 0.2 g). When the unit dose is 1 gram or more it should be written in grams (e.g., write 2 g, not 2000 mg).

Dispense only the necessary quantity of a drug to a patient. For example, if a patient is to take two tablets of a drug four times a day for 5 days, the total number of tablets to be dispensed would be 2 x 4 x 5 or 40 tablets. In order to discourage alterations in written prescription orders, when prescribing a controlled substance, in addition to writing the number of tablets or capsules to be dispensed, the amount must also be written-out longhand, e.g., Disp #20 (twenty).

Latin and other abbreviations (Table 6) are authorized in prescription writing.25 They save time and make alteration of a prescription by the patient more difficult. However, abbreviations are more likely to be misinterpreted and lead to potentially serious mistakes. Practitioners should avoid using abbreviations and write-out instructions in full. For example, an instruction for the patient should be written-out as follows: “Take two tablets four times a day for 5 days.”

Table 6. Common Latin abbreviations that may be used in prescription writing.25
AbbreviationFrom the LatinMeaning
a.c.ante cibumbefore meals
alt. h.alternis horisevery other hour
a.m.ante meridiemmorning, after noon
b.i.d.bis in dietwice daily
cap., caps.capsulacapsule
cccum ciboswith food
e.m.p.ex modo prescriptoas directed
h.s.hora somniat bed time
notc.nocteat night cibumafter meals meridiemevening or afternoon
prnpro re nataas needed
p.o.per osby mouth
q.a.d.quaque alternis dieevery other day
q.a.m.quaque die ante meridiemevery day before noon
q.h.quaque horaevery hour
q.h.s.quaque hora somnievery night at bedtime
q.1hquaque 1 horaevery 1 hour
q.d.quaque dieevery day
q.i.d.quarter in diefour time a day
qqhquarter quaque horaevery four hours
t.i.d.ter in diethree times daily
u.d., ut. dict.ut dictumas directed


The closing must exhibit the prescriber’s signature and DEA # (if applicable). It may also contain additional instructions to the pharmacist, e.g., whether generic substitution is allowed and/or to include warnings on container labels such as “May cause drowsiness,” “Take with food,” or “Do not take with grapefruit juice.” A pharmacist cannot refill a prescription without authorization, to avoid interrupting maintenance therapy, the prescriber may authorize refills on a written prescription.

Refills authorized on an order for a legend drug are valid for 1 year after the date of issue. For example, it is common practice to prescribe legend drugs for the treatment of a chronic condition such as hypertension to last for 90 days and to authorize three refills. An order for Schedule III, Schedule IV, and Schedule V drugs may be refilled up to five times within six months after the date of issue. Refilling orders for Schedule II drugs is prohibited, they require new prescriptions.