How Do I Keep Track of How Much Medicine Is Left in the MDI?

Question: How Do I Keep Track of How Much Medicine Is Left in the MDI?

Answer: Most metered dose inhalers don't have a built in counter. So it can be hard to know for sure how much medicine is left inside the canister. That can lead to using the MDI when it no longer contains enough medicine to be helpful.

So, it’s a good idea to have a system to keep track of how much medicine you have used. That way, you’ll know when to get your refill and avoid running out. Making sure you always have your asthma medicine on hand means better control of your symptoms and prevention of asthma attacks!

As soon as you get a new preventer medicine MDI, figure out how long it will last. The number of puffs, or doses, that an MDI contains is usually printed right on the canister. If you can't find it, ask your pharmacist to help you. Divide that number by the number of puffs per day that you use it. So, if a canister has 200 puffs and your prescription is for 2 puffs twice a day, then you'll divide 200 by 4 to get 50 days that it will last.

Next, use a calendar to see what date you'll run out. Mark that date on your canister so you'll know when to discard it. Even though it may still seem as though the MDI is dispensing medicine after that date, you can't be sure you're getting enough, if any, medicine after the stated number of doses.

You should also plan for when you need to get a refill. Count back a few days from when your canister will run out, and mark that date on your calendar as a reminder to get your refill before you run out.

For your rescue, or quick-relief, inhaler, that method won't work as well, because it's hard to know how many times a week you might need to use it. So a better method would be to keep a running count of the number of puffs you've taken. Keep a small notepad with your inhaler or mark it on your calendar.