From Milligrams to Tablets
Tablets per Dose = Prescribed Dose ÷ Strength of One Tablet
| Prescribed dose | Tablet strength | Tablets per dose | Note |
|---|---|---|---|
| 750 mg | 250 mg | 3 | Whole tablets |
| 20 mg | 10 mg | 2 | Whole tablets |
| 25 mg | 50 mg | 0.5 | Half a tablet; only if it may be split |
| 75 mcg | 50 mcg | 1.5 | One and a half; only if it may be split |
| 40 mg | 30 mg | 1.33 | Can't be made accurately; ask for another strength |
Then multiply by doses per day for tablets per day, and divide the bottle quantity by that to get the days supply.
Splitting Tablets Safely
Half-tablet doses are common and often fine, but not for every tablet:
- Usually OK: scored tablets (with a line across them) that your pharmacist confirms can be split.
- Usually not OK: extended-release (ER, XR, XL, SR), delayed-release or enteric-coated tablets. Splitting can release the dose too fast or destroy the coating.
- Capsules: don't open them unless the label or your pharmacist says you can. The calculator won't suggest half capsules.
Use a tablet splitter rather than a knife, and split one tablet at a time, just before you need it, unless your pharmacist says otherwise.
Same Unit on Both Sides
The prescribed dose and the tablet strength must use the same unit. Some medications are labeled in micrograms (mcg), for example thyroid medication.
- 1 mg = 1,000 mcg
- 0.1 mg = 100 mcg
- 1 g = 1,000 mg
If the calculator says you'd need more than 40 tablets for one dose, a unit mix-up is the likely cause.
When the Pharmacy Gives a Different Strength
Pharmacies sometimes dispense a lower strength and adjust the directions, for example "take 2 tablets" of a 10 mg tablet for a 20 mg dose, because of stock, cost or what your plan covers. The label is the instruction to follow. If the strength on a new bottle doesn't match what you had before, check with the pharmacist before taking it. Mix-ups between strengths are one of the more common medication errors at home.
To plan refills once you know your tablets per day, save the result to My Medications, or check a supply length with the 60-day or 90-day calculators.