Medication Days Supply Calculator

This medication days supply calculator will relieve you of the stress of having to manually calculate the number of days a patient’s medication will last in just 5 simple steps.

What is the Days Supply of a Drug?

Medication days supply is an estimate of the total number of days a prescribed drug will last for a patient based on the given dosage information.

It helps the pharmacist and healthcare provider ensure that the amount of drug dispensed for a patient will be enough for the intended duration of treatment, or till the next clinic visit.

It also helps to ensure adherence and prevent drug wastage since the patient knows that the amount of drug in their possession is only enough for the exact duration of treatment. As such, any loss or wastage will result in incomplete drug treatment which may harm therapy outcome.

Days supply also helps in cost management as the patient will only pay for the quantity needed for complete therapy. This eliminates excess remaining drugs which can contribute to drug overuse or abuse.

It also helps with insurance claims as most insurance companies place a quota on the amount of medications to be given to a patient at a given time.

How To Calculate Days Supply Of Medication?

Medication days supply is calculated by dividing the total amount of drug supplied by the total dose taken in a day. It can be represented by this formula:

Medication Days Supply = Total Amount of Drugs Supplied / (Quantity per dose X Frequency per day)

Where:

• Total Amount of Drugs Supplied is the total quantity of the drugs given to the patient. For example 100 tablets, 50 mL, 30 capsules, 5 vials, etc.
• Quantity per Dose is the amount of the supplied medication to be taken at a single time. For example 1 tablet, 2 capsules, 10 mL, etc.
• Frequency per Day is the number of times a prescribed dose will be taken in a day. For example 1 tablet TWO TIMES a day, 2 capsules ONCE a day, 5 mL THREE TIMES a day, etc.

Example Days Supply Calculation

To illustrate how days supply is calculated, let’s assume that a patient was supplied 14 tablets of Ibuprofen to be taken one tablet twice a day. The total quantity of drugs supplied here is 14, the quantity to be taken per dose is 1 tablet while the frequency per day is 2 times in a day.

Substituting the above values into the days supply formula will leave us with:

Days Supply = Total Number of Tablets Supplied / (Quantity per dose X Frequency per day)

Days supply = 14 / (1 x 2) days;

= 14/ 2 days;

= 7 days.

Hence the supplied quantity of ibuprofen will only last the patient for 7 days, assuming there is no form of loss.

How To Calculate Days Supply For Liquids?

Calculating the days supply of liquids such as oral solutions, suspensions, syrups, elixirs, etc. is not so different from that of tablets. It uses the same formula and follows the same pattern.

To calculate the days’ supply of liquids, you need to determine the total volume of the liquid drug supplied, and then the volume to be taken per dose as well as the frequency in a day. After that, all you have to do is substitute these values into the days supply formula below.

Days Supply = Total Volume of Liquid Supplied / (Volume per dose X Frequency per day)

For example, if a 236 mL Nyquil cough syrup is supplied to be taken 30 ml two times in a day. The total volume supplied here is 236 mL, the volume per dose is 30 mL while the frequency per day is 2 times.

By substituting these values into the above formula, you get 

Days Supply = 236 / (30 x 2) days;

= 236 / 60 days;

= ~ 4 days

How To Calculate Days Supply For Injections?

To calculate the days supply of injectables either in vials, ampoules, or bags. You need to determine the total amount supplied, the amount to be given per dose, and the number of times in a day that the drug will be administered. 

After getting those information ready, all that is left is to substitute these values into the days’ supply formula below:

Days Supply = Total Amount of Drugs Supplied / (Quantity per dose X Frequency per day)

To illustrate this, let’s assume that we supplied twelve 2ml ampoules of 150 mg/ml acetaminophen injection and we are to administer 600mg of the drug three times in a day. 

The total amount of injectables supplied here is 12 ampoules. The number of ampoules to be administered per dose is 2 ampoules (i.e. 300mg per ampoule), while the frequency of the dose is 3 times a day.

Substituting these values into the equation will result in:

Days Supply = 12 / (2 x 3) days;

= 12 / 6 days;

= 2 days.

Therefore, the supplied quantity of acetaminophen injection will only last for 2 days.

How To Calculate Days Supply For Inhaled Products?

To calculate the day supply for inhalers, you need to, first of all, determine the total number of actuations or puffs present in a single inhaler. 

This is often labeled on the drug package. After that, you multiply the number of actuations or puffs per dose by the frequency in a day and then use it to divide the total number of actuations in the inhaler.

For example, a Ventolin inhaler contains salbutamol sulfate as the active ingredient. Each canister of the inhaler contains 200 actuations and each puff or actuation contains 100 micrograms of salbutamol. 

If 1 ventolin inhaler is supplied, and the patient is to take 2 puffs three times a day. The total number of actuations in 1 inhaler is 200, the number of actuations per dose is 2, and the frequency per day is 3. 

The formula for days’ supply will be:

Days Supply = Total Number of Actuations in Inhaler Supplied / (Number of actuations per dose X Frequency per day)

Hence, it will take the patient 33 days to finish 1 canister of Ventolin inhaler at the prescribed dosage.

How To Calculate Days Supply For Eye Drops Or Ear Drops?

To calculate the days supply of ear or eye drops, you have to use the conversion factor of 20 drops per ml to determine the total volume per dose. After that, the rest is easy. Let’s assume we have 5 ml Ciprofloxacin eye drops and the patient is to instill one drop in both eyes two times a day.

The total volume of the drug supplied is 5 ml which contains 100 drops (5 ml x 20 drops). The volume per dose is 2 drops while the frequency is 2 times a day. Inserting these values into the formula below will see us arrive at:

Days Supply = Total Amount of Drops Supplied / (Total Drops per dose x Frequency per day)

Days Supply = 100 / (2 x 2) days;

= 25 days.

How To Calculate Days Supply For Insulin? 

To calculate the days supply of insulin, you have to first of all determine the total number of units dispensed per milliliter.

You can achieve this by multiplying the number of units per milliliter by the number of milliliters to be dispensed. The next step is to divide the total number of units supplied by the number of units to be administered per day.

For example, let’s assume that Lantus Solostar is prescribed to be taken 10 IU in the morning and 12 IU at night. Lantus solostar comes as 100 Units/mL and each pen is a 3 mL Unit. so, 1 solostar pen contains 300 IU of insulin. The total dose in a day will be 10 IU + 12 IU which is 22 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 / 22 days;

= 13.6 days