Enter the quantity of medication and the dosage per day into the calculator to determine the medication days supply.

Medication Days Supply Formula

The following formula is used to calculate the medication days supply:

DS = (Q * D) / F


  • DS is the medication days supply
  • Q is the quantity of medication
  • D is the dosage per day
  • F is the frequency of administration

To calculate the medication days supply, multiply the quantity of medication by the dosage per day, then divide the result by the frequency of administration.

What is a Medication Days Supply?

A Medication Days Supply refers to the estimated duration a prescribed medication will last for a patient based on the dosage instructions provided by the healthcare provider. It is calculated by dividing the total quantity of medication supplied by the number of times the medication is to be taken each day. For instance, if a patient is prescribed to take two tablets of a certain medication daily and is given a total of 60 tablets, the medication days supply would be 30 days. This concept is crucial in pharmacy practice as it helps in managing prescription refills, ensuring medication adherence, and avoiding medication shortages or overuse. It also aids in cost management and insurance claims as many insurance companies limit the number of days supply that can be dispensed at one time.

How to Calculate Medication Days Supply?

The following steps outline how to calculate the Medication Days Supply:

  1. First, determine the total quantity of medication available (Q). 
  2. Next, determine the prescribed dosage per day (D). 
  3. Next, gather the formula from above = MDS = Q / D.
  4. Finally, calculate the Medication Days Supply.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

total quantity of medication available (Q) = 120

prescribed dosage per day (D) = 3