ED, EOD, E3.5D, QW, BID: Dosing Shorthand Explained
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Dosing frequency abbreviations (ED, EOD, E3.5D, QW, BID)

Also called ED, EOD, E3.5D, E3D, QW, BID, TID, QD, QOD, twice weekly · Reviewed

Definition: Dosing frequency abbreviations are shorthand for how often a dose is taken. Some are old prescription Latin, like BID (twice a day). Others, like ED, EOD and E3.5D, are informal forum shorthand. Several are easy to misread, so medication safety groups recommend writing the schedule out in words.

What each one means

Prescription meanings from a formulary table and the ISMP list; forum terms marked informal.
ShorthandMeaningShots or doses per weekNote
EDEvery day7Informal
EODEvery other day3.5 on averageInformal
E3DEvery 3 daysAbout 2.33Informal
E3.5DEvery 3.5 days (twice a week)2Informal, for example Monday morning and Thursday evening
QWOnce a week1Common shorthand; write "weekly"
BIWTwice a week2ISMP: can be misread as twice a day
TIWThree times a week3ISMP: can be misread as three times a day
QDEvery day7ISMP and Joint Commission: do not use; misread as QID
QODEvery other day3.5ISMP and Joint Commission: do not use; misread as daily
BID / TID / QIDTwice / three times / four times a day14 / 21 / 28Prescription Latin

Worked example: same weekly total, different schedules

Splitting a 100 mg weekly total (arithmetic only)

  1. QW: 100 ÷ 1 = 100 mg per shot.
  2. E3.5D: 100 ÷ 2 = 50 mg per shot.
  3. EOD: 100 ÷ 3.5 = about 28.6 mg per shot.
  4. ED: 100 ÷ 7 = about 14.3 mg per shot.
  5. Note that EOD does not fit a 7-day week: shots land on a different weekday each week, and a year of EOD is about 365 ÷ 2 = 182 or 183 shots.

This is division, not a recommendation. Your schedule comes from your prescriber or label.

Common mix-ups

  • Twice a week vs twice a day. BIW and BID differ by a factor of 7. Write the words.
  • E3.5D is not every 3 days. E3D gives about 2.33 shots a week; E3.5D gives exactly 2.
  • EOD drifts. Because it skips weekdays, reminders tied to a fixed weekday will not match it.

Read more on Dose Track: Weekly vs twice-weekly TRT injections · Missed dose guides

General education drawn from labels and published studies, not personal medical advice. Your prescriber, pharmacist and the label that came with your product are the final word.
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Frequently asked questions

What does E3.5D mean?+
Every 3.5 days, which is twice a week. A common pattern is one dose early in the week and one about three and a half days later.
Is EOD the same as three times a week?+
No. EOD averages 3.5 doses a week and shifts weekdays. Three times a week, such as Monday, Wednesday and Friday, is a fixed 3.
Why should I avoid writing QD or QOD?+
The ISMP list says QD can be misread as four times a day and QOD as daily. Both are on the Joint Commission do-not-use list, so write daily or every other day.

Sources

  1. ISMP List of Error-Prone Abbreviations, Symbols, and Dose Designations (2024)
  2. Carpenter JW (ed). Exotic Animal Formulary, Elsevier 2018: table of prescription abbreviations (PMC7151815)

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