How Do I Read Dosage and Units in a Chinese Oncology Prescription?
A Chinese oncology prescription contains three pieces of information that must be read together: the dose (how much), the frequency (how often), and the duration (for how long). Reading one without the others — or mistaking a unit or abbreviation — can change the actual amount of drug you receive. This page explains the standard abbreviations and units, and the points where errors most commonly occur.
Quick Answer
Chinese oncology prescriptions use standard metric units (g = gram, mg = milligram, ml = milliliter) and Latin-derived frequency abbreviations (qd = once daily, bid = twice daily, tid = three times daily, qid = four times daily). The most dangerous misreadings are unit confusion (mg vs g) and frequency confusion (qd vs bid, or “three times daily” vs “every 8 hours”). A dose written as “500mg tid” is not the same as “500mg q8h” — the first means three doses during waking hours, the second means a dose every 8 hours around the clock. Always confirm the unit, the frequency, and the duration together, and ask the prescribing team or hospital pharmacist to clarify any part you are unsure about.
“If I can read the numbers, I can understand the dose.” — No. The number means nothing without its unit, and the unit means nothing without its frequency. 500 mg once daily and 500 mg three times daily are not the same prescription. 500 mg and 500 g are not the same amount. The prescription is a complete instruction, not a collection of separate numbers.
Who This Page Is NOT For
This page is not a tool to calculate or verify your own dose, and it is not a substitute for the explanation given by the prescribing physician or hospital pharmacist. It is for patients and families who have received a Chinese oncology prescription and want to understand its structure and terminology — so they can ask better questions of the prescribing team. Only the prescribing physician and the hospital pharmacist can confirm what you should take, how much, and how often.
The Three Elements of a Prescription Instruction
Every prescription instruction has three parts. Reading them together is essential.
1. 剂量 — Dose (how much)
The amount of drug per administration, usually expressed with a unit (mg, g, ml).
- Example: 500mg
- Unit matters: mg ≠ g
- May be per kg body weight in oncology
2. 频次 — Frequency (how often)
How many times per day, or at what interval, the dose should be taken.
- qd = once daily
- bid = twice daily
- tid = three times daily
- qid = four times daily
3. 疗程 — Duration (for how long)
How many days, weeks, or cycles the prescription should continue.
- Example: 7d = 7 days
- Example: 21d = 21 days (one cycle)
- May be expressed as “× 3 cycles”
Standard Units and Frequency Abbreviations
| Abbreviation / unit | Meaning | Note |
|---|---|---|
| g | gram | 1 g = 1000 mg |
| mg | milligram | 1 mg = 0.001 g |
| ml | milliliter | Volume, often for liquids or infusions |
| qd | Once daily | From Latin quaque die |
| bid | Twice daily | From Latin bis in die |
| tid | Three times daily | From Latin ter in die |
| qid | Four times daily | From Latin quater in die |
| q8h | Every 8 hours | Around the clock, not “three times during waking hours” |
| q12h | Every 12 hours | Around the clock |
| prn | As needed | From Latin pro re nata |
| po | By mouth / orally | From Latin per os |
| ivgtt | Intravenous drip / infusion | Common in oncology |
Dangerous Misreadings
mg vs g
A 1000-fold difference. A dose written as “500mg” is 0.5 g. A dose written as “500g” is 500,000 mg. Confusing the two is a critical error.
qd vs bid
“Once daily” vs “twice daily.” Reading qd as bid doubles the daily dose. Reading bid as qd halves it.
tid vs q8h
“Three times daily” vs “every 8 hours.” For most drugs, three times during waking hours is close to every 8 hours, but not identical. For some drugs, the interval is specified for a reason.
Duration: 7d vs 7 cycles
“7 days” vs “7 cycles.” A cycle may be 21 or 28 days. Confusing days and cycles can lead to continuing treatment far longer than intended.
A Fictional Example: Reading a Prescription Line
The example below is fictional. It is used only to show how the three elements appear on a prescription line. It is not derived from any real patient’s records.
How to read this example: “奥希替尼片” is the drug name (osimertinib tablet). “80mg” is the dose per administration. “po” means by mouth. “qd” means once daily. “× 30d” means for 30 days. Reading it together: 80 mg by mouth once daily for 30 days. If you read “qd” as “bid,” you would double the daily dose. If you read “80mg” as “80g,” you would be off by a factor of 1000. The three elements — dose, frequency, duration — must be read together, not separately.
Questions to Bring to the Prescribing Team or Pharmacist
These questions are educational. They are not an assessment of your prescription. Review the answers with the prescribing physician or hospital pharmacist.
What is the exact dose per administration, and in what unit?
Ask for the number and the unit (mg, g, ml) together, and confirm which unit is written on the prescription.
How many times per day, and is there a specific interval?
Ask whether the frequency is “three times daily” or “every 8 hours” — the two are not always interchangeable.
For how many days or cycles should I take this?
Ask whether the duration is expressed in days or cycles, and what the cycle length is.
Is the dose calculated per body weight or body surface area?
If so, ask whether the calculation has been done for your specific measurements.
What should I do if I miss a dose?
Ask for the specific instruction for this drug — missing a dose is not handled the same way for every medication.
Continue Your Research
Related reference pages on Chinese medical documents and cancer treatment.
How Do I Match a Chinese Drug Name to Its Generic Name?
Identify a Chinese cancer drug by brand, active ingredient, or generic name.
What Do the Terms in a Chinese Discharge Summary Mean?
The document you hand to your home oncologist — diagnosis, procedures, medications, and follow-up.
What Do the Terms in a Chinese CAR-T Treatment Record Mean?
Product names, cell types, complications, and follow-up terms.
Frequently Asked Questions
What does “qd” mean, and how is it different from “bid”?
“qd” means once daily (from Latin quaque die). “bid” means twice daily (from Latin bis in die). Reading qd as bid would double the daily dose; reading bid as qd would halve it. Always confirm the frequency abbreviation with the prescribing team if you are unsure.
Is “tid” the same as “every 8 hours”?
Not exactly. “tid” means three times during the day (usually waking hours). “q8h” means every 8 hours around the clock. For most drugs, the difference is small, but for some drugs the interval is specified for a clinical reason. If the prescription uses an interval abbreviation (q8h, q12h), follow the interval. If it uses a daily-count abbreviation (tid), ask whether the waking-hours interpretation is intended.
What is the difference between mg and g?
1 gram (g) = 1000 milligrams (mg). A dose written as “500mg” is half a gram. A dose written as “500g” is 500,000 milligrams. Confusing the two is a 1000-fold error. Always check the unit written on the prescription.
Why does the dose say “mg/m²” or “mg/kg”?
In oncology, many drugs are dosed per body surface area (mg/m²) or per kilogram of body weight (mg/kg), not as a fixed amount. This is because the appropriate dose depends on the patient’s size. The calculation is done by the treating team using your height, weight, and other factors. If you see “mg/m²” or “mg/kg” on the prescription, the actual dose you receive has been calculated for you — ask the treating team to confirm the calculation.
What does “× 21d” mean, and is it the same as one cycle?
“× 21d” means “for 21 days.” In oncology, 21 days is a common cycle length, but not every 21-day period is a cycle, and not every cycle is 21 days. If the prescription says “× 21d,” it means the drug is taken for 21 days. If it says “× 1 cycle (21d),” it means one cycle of 21 days. Ask the treating team to clarify whether a rest period follows.
Where can I find the full list of Chinese medical document reference pages?
This page is part of a series of question-based reference pages on Chinese medical documents. Related pages cover pathology certainty terms, drug-name matching, high-risk mistranslation terms, discharge summaries, laboratory reports, CAR-T records, imaging reports, clinical trial documents, and molecular reports. You can find the full list on the Evidence Hub.
Sources & References
- 安安网（国家药品监督管理局）. 如何识读医生处方？2018-02-25. (Includes standard prescription abbreviations: g, mg, ml, qd, bid, tid, qid, qn, q2h, q8h.) anan.gov.cn ↗
- 武汉市中心医院. 如何识读医生的处方？2017-12-29. (Includes frequency abbreviations and their Latin origins.) zxhospital.com ↗
- Australian Commission on Safety and Quality in Health Care. Recommendations for terminology, abbreviations and symbols used in medicines documentation. 2016. (Provides safe terms and abbreviations for dose frequency, including qid, and warns against ambiguous abbreviations.) safetyandquality.gov.au ↗
- Nationwide Children’s Hospital. How to Read a Prescription Label. 2024-07-25. (Explains medication strength, instructions, and duration on a prescription label.) nationwidechildrens.org ↗