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newSchoolWorks.com › VoTechWorks › Health & Personal Services › Pharmacy Technician › Pharmacy Calculations and Order Entry › Lesson 4
HLT-PHAR41-03 · Lesson 4 · 15 clock hours · theory

Reading the prescription: parts, sig codes and abbreviations

Objective. Identify every required element of a prescription and translate sig codes into plain directions for the label.

⚠ Pending professional review

This lesson, its worked examples and its practice questions has not yet been verified by a licensed pharmacist or by a certification or approval body. It is a study draft and may contain errors. Do not use it to make decisions about any patient or medication. Always follow your instructor, your supervising professional, and current official references and regulations.

VoTechWorks program approval and accreditation are still in progress. Credentials are issued only by the certifying bodies named in each program, after their own exams.

Why Prescriptions Have Rules

Every prescription is a legal document and a communication tool between the prescriber and the pharmacy. A single missing element or misread abbreviation can cause the wrong drug, dose, or directions to reach a patient. As a pharmacy technician, your first job at the order-entry station is to confirm that a prescription is complete and then translate its coded language into clear, plain directions for the dispensing label.

Required Elements of a Valid Prescription

Federal law and state boards of pharmacy require specific information on every prescription. Learn these elements so you can spot what is missing before a pharmacist checks the order.

1. Patient information – Full name, date of birth (or age), and address. Date of birth helps verify the correct patient and flags pediatric or geriatric dosing concerns.

2. Date written – The date the prescriber signed the order. Most states limit how long a prescription remains valid (commonly six months for non-controlled drugs; schedules II–V have stricter limits).

3. Drug name – Brand or generic. A prescriber may write "DAW" (dispense as written) to prohibit generic substitution.

4. Strength – For example, 500 mg, 0.1%, or 10 mg/5 mL. Without a strength, the pharmacist cannot verify that the correct product is dispensed.

5. Dosage form – Tablet, capsule, solution, cream, inhaler, etc. Some drugs are available in multiple forms.

6. Quantity – The total amount to dispense: number of tablets, milliliters, grams, or inhalers. Often written as #30, 120 mL, or 15 g.

7. Sig (signa) – Latin for "write" or "label." This field contains the directions coded with abbreviations. Translating the sig accurately is the central skill of this lesson.

8. Refills – The number of times the prescription may be refilled. Schedule II drugs may never be refilled; Schedules III–IV are limited to five refills within six months under federal law.

9. Prescriber information – Name, address, phone number, and DEA number (required for controlled substances). The DEA number also appears on the prescription for easy verification.

10. Prescriber signature – A valid, handwritten signature (or an authorized electronic equivalent) makes the order legal.

If any required element is absent, technicians must contact the prescriber or their office—they cannot fill in missing clinical information themselves.

The Sig: Decoding Latin Abbreviations

The sig is written in a shorthand that evolved from Latin. Pharmacies across the United States use the same core set of abbreviations, so learning them once serves you everywhere.

Route of administration

| Abbreviation | Meaning |

|---|---|

| po | by mouth (per os) |

| sl | sublingual (under the tongue) |

| top | topically |

| au / ad / as | each ear / right ear / left ear |

| ou / od / os | each eye / right eye / left eye |

| pr | rectally |

| iv | intravenous |

| im | intramuscular |

| sq or sc | subcutaneous |

Frequency

| Abbreviation | Meaning |

|---|---|

| qd or q.d. | every day (once daily) |

| bid | twice a day |

| tid | three times a day |

| qid | four times a day |

| qhs | every bedtime |

| q4h | every 4 hours |

| q6h | every 6 hours |

| q8h | every 8 hours |

| prn | as needed |

| ac | before meals |

| pc | after meals |

| hs | at bedtime |

Dose quantity

| Abbreviation | Meaning |

|---|---|

| tab | tablet |

| cap | capsule |

| tsp | teaspoon (5 mL) |

| tbsp | tablespoon (15 mL) |

| gtt | drop(s) |

| ss | one-half |

| i, ii, iii | 1, 2, 3 (Roman numerals) |

The ISMP Do-Not-Use List

The Institute for Safe Medication Practices (ISMP) identifies abbreviations that cause errors. Technicians must recognize these dangerous abbreviations when they appear on incoming orders and flag them for the pharmacist:

Putting It Together: Sig Translation

When you read a sig, work left to right: dose quantity → dosage form → route → frequency → special instructions.

Example sig: ii tab po bid pc prn pain

Translation: Take 2 tablets by mouth twice a day after meals as needed for pain.

Always write label directions in plain, patient-friendly language—avoid medical jargon on the dispensing label.

Controlled Substance Prescriptions

Schedule II prescriptions require a hard-copy, hand-signed original in most situations (electronic prescribing for controlled substances, EPCS, is permitted in most states but has additional security requirements). Schedule II prescriptions cannot be refilled; a new prescription is required each time. Schedules III and IV allow up to five refills within six months; Schedule V rules vary by state but are generally less restrictive.

Summary Checklist for Order Entry

1. Confirm all ten required elements are present.

2. Check the date—is the prescription expired?

3. Identify the drug, strength, and form.

4. Translate the sig completely and accurately.

5. Verify the quantity matches the sig and days supply.

6. Note refill authority and controlled-substance schedule.

7. Flag any ISMP do-not-use abbreviations for the pharmacist.

Mastering these steps protects patients and keeps your pharmacy legally compliant.

Key terms8

Signa (sig)The section of a prescription containing abbreviated directions that tell the patient how to use the medication; derived from the Latin word meaning 'write' or 'label.'
DAW (dispense as written)A prescriber notation instructing the pharmacy to dispense the brand-name drug and not substitute a generic equivalent.
DEA numberA unique identifier issued by the Drug Enforcement Administration that authorizes a practitioner to prescribe controlled substances.
PRNAbbreviation from Latin pro re nata meaning 'as needed'; indicates the patient should take the medication only when a specific condition (such as pain or nausea) is present.
Days supplyThe number of days a dispensed quantity of medication will last when taken exactly as directed; used for billing and refill scheduling.
ISMP Do-Not-Use listA list published by the Institute for Safe Medication Practices identifying abbreviations, symbols, and dose designations that are prone to misinterpretation and should be avoided in medication orders.
Schedule IIThe most restrictive category of prescribable controlled substances under the Controlled Substances Act; these drugs have high potential for abuse and dependence and cannot be refilled.
Trailing zeroA zero written after a decimal point (e.g., 1.0 mg) that is considered dangerous because the decimal point may be overlooked, leading to a tenfold dosing error.

Worked examples4

1. Translate this sig into plain label directions: 'i cap po tid pc'
  1. Identify dose quantity: i = 1; cap = capsule.
  2. Identify route: po = by mouth.
  3. Identify frequency: tid = three times a day.
  4. Identify timing modifier: pc = after meals.
  5. Combine all elements in plain language.
Answer: Take 1 capsule by mouth three times a day after meals.
2. Calculate the days supply: the sig reads 'i tab po bid' and the quantity dispensed is 60 tablets.
  1. Determine tablets used per day: 1 tablet × 2 times per day = 2 tablets per day.
  2. Divide total quantity by daily use: 60 tablets ÷ 2 tablets per day = 30 days.
  3. State the days supply.
Answer: Days supply = 30 days.
3. Calculate the days supply: the sig reads 'ii tsp po q6h prn cough' and the quantity dispensed is 240 mL. Assume the patient takes every dose as directed (worst-case fill).
  1. Convert dose to mL: 1 tsp = 5 mL; 2 tsp = 10 mL per dose.
  2. Determine doses per day at q6h: 24 hours ÷ 6 hours = 4 doses per day.
  3. Calculate mL used per day: 10 mL × 4 doses = 40 mL per day.
  4. Divide total quantity by daily use: 240 mL ÷ 40 mL per day = 6 days.
  5. State the days supply.
Answer: Days supply = 6 days (at maximum use).
4. A prescription reads: 'Amoxicillin 250 mg/5 mL suspension, sig: ii tsp po tid × 10 days. Dispense: qs.' How many total milliliters should be dispensed?
  1. Convert dose to mL: 2 tsp × 5 mL per tsp = 10 mL per dose.
  2. Determine doses per day: tid = 3 doses per day.
  3. Calculate mL per day: 10 mL × 3 = 30 mL per day.
  4. Multiply by duration: 30 mL per day × 10 days = 300 mL total.
  5. State the quantity to dispense.
Answer: Dispense 300 mL of amoxicillin 250 mg/5 mL suspension.

The math in this lesson1

Learners translate sig codes and compute tablets used per day from the directions.
6.RP.3
In class: Sig translation drill · Missing-element hunt · Label-writing practice
Materials: Sample prescriptions, sig-code reference
Check: Quiz ≥ 90%

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

Federal Requirements
1. A prescription is presented without a prescriber DEA number. Which drug category makes this omission a legal problem that prevents dispensing?
Order Entry and Processing
2. The sig on a prescription reads 'gtt ii ou bid.' What are the correct label directions?
Patient Safety and Quality Assurance
3. A technician receives a prescription written for '1.0 mg' of a medication. Why should this be flagged before dispensing?
Federal Requirements
4. A patient brings in a prescription for a Schedule III medication dated seven months ago. How should the technician handle this?
Order Entry and Processing
5. The sig reads 'i tab po qid prn pain.' The quantity dispensed is 120 tablets. What is the maximum days supply if the patient takes every allowed dose?
Federal Requirements
6. Which of the following is a required element on every prescription regardless of whether the drug is a controlled substance?
Order Entry and Processing
7. A prescriber writes 'DAW' on a prescription. What action does this require from the pharmacy?
Patient Safety and Quality Assurance
8. A technician notices the sig contains the abbreviation 'U' for units. According to the ISMP Do-Not-Use list, why is this abbreviation considered dangerous?
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