Using a metered dose inhaler (MDI) correctly takes a specific sequence of steps, and getting them wrong is extremely common. Studies show that roughly 45% of people mistime the puff with their breath, 44% breathe in too fast, and 46% skip the breath-hold afterward. Each of these mistakes means less medication reaches your lungs. Here’s how to get the full dose every time.
Prime Your Inhaler First
Before you use a brand-new inhaler, or one that’s been sitting unused for a few weeks, you need to prime it. Priming clears the valve and ensures the first puff delivers a full, consistent dose rather than a burst of propellant with little medication. To prime, shake the inhaler well, point it away from your face, and press down to release a spray into the air. Repeat this for the number of test sprays listed in your inhaler’s instructions, as different medications require different amounts.
You don’t need to prime before every use. Only prime when the inhaler is new or has gone unused for the timeframe specified on its packaging (typically a few weeks).
Step-by-Step Technique
Stand or sit upright. Good posture opens your airways and helps you take a fuller breath.
Shake the canister for about five seconds. The medication inside is a suspension, and shaking mixes it evenly with the propellant so each puff delivers the right amount.
Breathe out fully. Before putting the inhaler to your mouth, exhale gently and completely. This empties your lungs so there’s more room for the medicated air to travel deep into your airways.
Seal your lips around the mouthpiece. Place the mouthpiece between your teeth, close your lips tightly around it, and keep your tongue out of the way so it doesn’t block the spray.
Press and breathe in slowly. As you start to breathe in, press down on the canister once. The key detail most people get wrong is speed: your inhalation should be slow and steady, lasting about 3 to 5 seconds. A fast, sharp breath (the kind that feels natural) actually sends most of the medication crashing into the back of your throat instead of carrying it deep into your lungs. Think of it as sipping air through a straw, not gasping.
Hold your breath. Once your lungs are full, remove the inhaler from your mouth and hold your breath for 5 to 10 seconds. This gives the tiny medication particles time to settle onto the walls of your airways, where they’re absorbed. Breathing out immediately lets much of the medication float right back out.
Breathe out gently through your nose or pursed lips.
Taking a Second Puff
If your prescription calls for two puffs, wait 30 to 60 seconds before the next one. Shake the inhaler again before each puff. This waiting period lets the valve reset and ensures the second dose is as accurate as the first. Then repeat the full sequence: exhale, seal, press, slow inhale, breath-hold.
Why a Spacer Makes a Big Difference
A spacer (also called a valved holding chamber) is a tube that attaches between the inhaler and your mouth. It solves the two most common problems with MDI technique: coordination and speed.
Without a spacer, you have to press the canister and breathe in at almost the exact same moment. Mistiming by even half a second means medication hits your tongue or throat instead of your lungs. A spacer holds the medication cloud in a chamber for a few seconds, so you can press the canister first and then inhale at your own pace. It also slows the spray down, which naturally encourages the slow, steady breath you need.
If you struggle with coordination, if your child uses an inhaler, or if you use a corticosteroid inhaler (which can cause mouth irritation), a spacer is worth using every time. For children under about 4 years old, a spacer with a face mask is recommended because they can’t form a reliable seal around a mouthpiece. Around age 4, most children can switch to a spacer with a mouthpiece only.
If you didn’t get a full breath while using a spacer, you can inhale a second time from the chamber and hold your breath again for about 5 seconds to capture any remaining medication.
Cleaning Your Inhaler
Medication residue builds up inside the plastic actuator (the colored housing around the canister) over time, and that buildup can partially block the spray. Clean it at least once a week with this process:
- Remove the metal canister and set it aside. Never get the canister wet.
- Take the cap off the mouthpiece.
- Run warm water through the mouthpiece for about 30 seconds, then through the top opening for another 30 seconds.
- Wipe the mouthpiece with a clean cotton cloth.
- Let everything air dry completely before reassembling. Putting a wet actuator back together can clog the valve.
- Reassemble and prime by pressing down three times with the inhaler pointed away from you, then replace the cap.
Knowing When Your Inhaler Is Empty
This is trickier than it seems. An MDI canister contains far more propellant than medication. The inactive propellant makes up 95 to 99 percent of the canister’s contents, so an inhaler that’s run out of medicine will still spray what looks and feels like a normal puff. You can press the canister dozens of times past its labeled dose count and get nothing but propellant.
If your inhaler has a built-in dose counter, use it. That number is the most reliable way to know how many doses remain. If it doesn’t have a counter, the only accurate method is to track each puff yourself. Write down the total number of doses on the label, mark each use, and replace the inhaler when you’ve reached that number.
The old advice about floating the canister in water to check its level is no longer recommended. The FDA has noted that this “float test” is unreliable and can actually damage the inhaler’s valve mechanism.
Common Mistakes That Reduce Your Dose
Three errors account for the vast majority of poor inhaler technique, and they’re all fixable:
- Breathing in too fast. A quick, deep gasp deposits medication in your throat. Slow your inhalation to 3 to 5 seconds. If you hear a whistling sound from your spacer, you’re breathing too fast.
- Poor coordination. Pressing the canister before or after you start inhaling wastes medication. Using a spacer eliminates this problem entirely.
- Skipping the breath-hold. Even a 5-second hold after inhaling significantly increases how much medication settles into your airways. It’s the easiest step to forget and one of the most important.
If you use a corticosteroid inhaler (commonly prescribed as a daily controller for asthma), rinse your mouth with water and spit it out after each use. This prevents the medication from lingering in your mouth and throat, where it can cause irritation or fungal infections.