09/04/2026
This inhaler trick makes perfect sense… until you realize it doesn’t actually work.
For years, people have been told to drop their inhaler canister into water.
If it sinks, there’s medication left.
If it floats, it’s empty.
Easy enough.
Except your inhaler wasn’t designed to be a pool toy.
Different inhalers use different canisters, propellants, weights, and designs. That means how high or low a canister floats does NOT reliably tell you how many usable doses remain.
And some manufacturers specifically tell you not to put the canister in water.
So how ARE you supposed to know when your inhaler is running out?
First, check for a dose counter.
If your inhaler has one, use it. That little number is much more useful than anything a glass of water is going to tell you.
No dose counter?
Check how many doses your inhaler contains when new.
Then keep track of your puffs.
If your inhaler contains 200 doses and you take 4 puffs every day, you have roughly 50 days of medication.
For rescue inhalers, it gets trickier because you may use 2 puffs today and none for the next week.
That’s why I recommend keeping track of your use and having a replacement available before you think you’re completely out.
And here’s something many people don’t realize:
Don’t judge your inhaler by whether it still sprays.
Something coming out of the mouthpiece does NOT necessarily mean you’re still receiving the expected medication dose.
So yes, I dropped a bunch of inhaler canisters into water.
But I did it to make one point:
Your asthma medication is too important to measure by whether it sinks or swims.
Use the dose counter. Track your doses. And if you’re not sure, bring the inhaler to your pharmacist.
Follow Alex Mihaila, R.Ph., MBA | Medication Safety Pharmacist for medication advice that makes sense outside the pharmacy too.
