The MDI medical abbreviation most often means metered dose inhaler, a small pressurized canister that releases a measured amount of medicine as a spray each time it is pressed. People usually call it an inhaler or a puffer, and it is used for asthma, COPD and other breathing conditions.
In diabetes clinics the same letters can mean multiple daily injections, an insulin routine with several shots a day. Context nearly always settles which one is meant: an MDI next to a lung drug and the word puffs is an inhaler, while MDI next to insulin is the injection plan. Below are sample lines, the parts of the device, and the other inhaler types it is compared with.
At a glance
Stands for
Metered dose inhalerOther meanings
Multiple daily injections (insulin therapy)Used in
Asthma, COPD, other airway diseasesDose unit
Puffs, also called actuations or inhalationsOften paired with
A spacer or valved holding chamberDo not confuse with
DPI (dry powder inhaler) and nebulizer
What the MDI medical abbreviation describes
A metered dose inhaler has three main parts: a metal canister holding the medicine and a propellant, a plastic mouthpiece called the actuator, and a valve that measures out the same amount with each press. Pressing the canister releases one puff, which the user breathes in slowly and deeply so the medicine reaches the airways rather than the back of the throat.
Many inhalers have a dose counter on the side. Others need the user to keep track. Most need priming, a few test sprays into the air, when they are new or have not been used for a while; the leaflet for each product gives the number.
Reading an inhaler order line
| Piece | Plain meaning |
|---|---|
| Albuterol | A quick relief medicine that opens the airways |
| MDI | Given from a metered dose inhaler |
| 2 puffs inhaled | Two presses, each breathed in |
| q4h | No more often than every 4 hours |
| PRN wheeze | Only when needed for wheezing |
| with spacer | Use a holding chamber attached to the mouthpiece |
Clinic note: "Fluticasone MDI 2 puffs BID, rinse mouth after use." This is a daily controller inhaler taken twice a day. Rinsing removes steroid left in the mouth. The example shows the format only.
Spacers and technique
A spacer is a tube that fits on the mouthpiece. The puff goes into the tube first, and the person breathes it in from there. This means hand and breath do not need perfect timing, and less medicine lands in the mouth. A valved holding chamber is a spacer with a one way valve; children often use one with a face mask.
Technique matters more than people expect. Nurses and pharmacists often ask patients to show how they use the inhaler, then coach small fixes such as shaking it first, breathing out before the puff, and holding the breath for a few seconds afterward.
MDI compared with other inhaled devices
| Device | How it works | What the user does |
|---|---|---|
| MDI | Propellant sprays a measured dose | Press and breathe in slowly |
| DPI, dry powder inhaler | Releases powder when the user inhales | Breathe in fast and hard |
| Soft mist inhaler | Slow moving mist without propellant | Press and breathe in slowly |
| Nebulizer | Machine turns liquid into a fine mist | Breathe normally through a mask or mouthpiece for several minutes |
Because the breathing styles differ, someone switched from one device to another usually needs fresh teaching.
The other MDI: multiple daily injections
In diabetes care, MDI describes an insulin plan with a long acting basal shot once or twice a day plus mealtime shots of rapid acting insulin. It is often compared with insulin pump therapy. A note might read "Type 1 DM on MDI, considering pump." Nothing about an inhaler is involved there.
If a record could mean either, look at the drug name next to it. An inhaled drug points to the device; insulin points to the injection plan.
Questions to bring to the pharmacy counter
- Is this a rescue inhaler, a daily controller, or both?
- Does it need priming, and how many test sprays?
- How will I know when it is close to empty?
- Should I use a spacer with it?
More route and dosing shorthand, including the inhaled forms, is gathered in the prescription abbreviation section.
This page offers reading help only. Your own inhaler plan, including which puffer to use when, comes from your prescriber and can be reviewed with your pharmacist.
Frequently asked questions
What does MDI stand for in medicine?
It usually stands for metered dose inhaler, a pressurized puffer that gives a set dose with each press. In diabetes care it can also mean multiple daily injections of insulin.
Is an MDI the same as an inhaler?
An MDI is one kind of inhaler. Dry powder inhalers and soft mist inhalers are other kinds, and each needs a different breathing technique.
What is the difference between an MDI and a nebulizer?
An MDI is a handheld canister used in a few seconds. A nebulizer is a machine that turns liquid medicine into mist, breathed in over several minutes. Either can deliver some of the same drugs.
Why use a spacer with an MDI?
A spacer holds the puff so it can be breathed in without exact timing. It also helps more medicine reach the lungs and less settle in the mouth and throat.