This handy medication days supply calculator takes the guesswork out of determining how long a medication supply will last by doing the math for you in just 5 quick steps. Try it out below and see for yourself!
Medication Days Supply Calculator
How to Use This Medication Days Supply Calculator
- Select the dosage form (tablets/capsules, liquid/cream, etc.)
- Enter the total quantity dispensed.
- Input the dose amount to be taken each time.
- Choose the daily dosing frequency (once, twice, three times, etc.)
- Click “calculate days supply.“
That’s it! The calculator will crunch the numbers based on the dosage details you provided, giving you the exact number of days that particular supply should last the patient. No more manual calculations needed.
What is the Days Supply of a Drug?
The days supply of a medication refers to an estimate of the total number of days the prescribed drug will last the patient based on the provided dosage information.
Days supply is very important because it helps the healthcare provider to ensure that the prescribed drug is in a quantity that will be sufficient enough for the patient throughout the treatment duration, or at least till the next clinic day.
How To Calculate Days Supply Of Medication
The days supply is calculated by dividing the total quantity of medication dispensed by the total daily dosage amount.
Days supply can be calculated using this formula:
Days Supply = Total Quantity Supplied / (Dose Per Time x Frequency Per Day)
Where:
- Total Quantity Supplied is the number of units dispensed (e.g. 100 tablets)
- Dose Per Time is the amount taken each time (e.g. 2 tablets)
- Frequency Per Day is how many times per day it’s taken (e.g. twice daily)
For example, if dispensed 30 tablets of a medication to be taken as 1 tablet twice daily.
Days Supply = 30 tablets / (1 tablet x 2 times per day)
Days Supply = 30 tablets / 2 tablets per day
Days Supply = 15 days
So, a supply of 30 tablets with directions to take 1 tablet twice daily would last for a 15 day period.
How To Calculate Days Supply For Liquids
Calculating days supply for liquid medications follows the same principles as solid dosage forms like tablets. You’ll need to know the total volume dispensed, the volume for each dose, and how many times per day it’s taken.
The formula is:
Days Supply = Total Volume Dispensed / (Volume Per Dose x Frequency Per Day)
For example, if dispensed 236mL of cough syrup to take 30mL twice daily.
Days Supply = 236mL / (30mL x 2 times per day)
= 236mL / 60mL per day
= 4 days supply
How To Calculate Days Supply For Injections
For injectable medications, you’ll need to determine the total number of vials/ampules and the dose amount versus volume.
Days Supply = Total Number of Vials/Ampules / (Number Per Dose x Frequency Per Day)
If dispensed 12 ampules of 150mg/mL acetaminophen injection to give 600mg (4 ampules) three times daily:
Days Supply = 12 ampules / (4 ampules x 3 times per day)
= 12 ampules / 12 ampules per day
= 1 day supply
How To Calculate Days Supply For Inhaled Products
To calculate the days supply for inhalers, you’ll need to determine the total number of actuations (puffs) in the inhaler, which is typically labeled on the packaging.
Then, use this formula:
Days Supply = Total Actuations in Inhaler / (Actuations Per Dose x Frequency Per Day)
For example, if a Ventolin inhaler contains 200 total actuations and the dose is 2 actuations three times daily:
Days Supply = 200 actuations / (2 actuations x 3 times per day)
= 200 actuations / 6 actuations per day
= 33 days supply
Hence, one inhaler with 200 actuations will last 33 days when taking 2 puffs three times per day.
How To Calculate Days Supply For Eye/Ear Drops
For ophthalmic or otic drop medications, you’ll need to first convert the volume to number of drops using 20 drops = 1mL.
Then the formula is:
Days Supply = Total Drops in Bottle / (Drops Per Dose x Frequency Per Day)
If dispensed 5mL (100 drops) of ciprofloxacin eye drops to use 1 drop in each eye twice daily:
Days Supply = 100 drops / (2 drops x 2 times per day)
= 100 drops / 4 drops per day
= 25 days supply
Therefore, a 5mL bottle with instructions for 1 drop each eye twice daily will last 25 days.
How To Calculate Days Supply For Insulin
To calculate the days supply of insulin, first of all determine the total number of units dispensed per milliliter.
Total number of units dispensed per milliliter can be calculated by multiplying the number of units per milliliter by the number of milliliters to be dispensed. After this, proceed to divide the total number of units supplied by the number of units to be administered per day.
For example, assuming you were prescribed a Lantus Solostar to be administered 8 IU in the morning and 10 IU at night. Lantus solostar comes as 100 Units/mL and each pen is a 3 mL Unit. Hence, 1 solostar pen contains 300 IU of insulin. The total dose in a day will be 8 IU + 10 IU which is 18 IU.
Using the formula below, the days supply can be calculated to be:
Days Supply = Total Amount of Units Supplied / Total amount of units to be used per day
= 300 / 18 days;
= 16.6 days