How does inhaled insulin (Afrezza) differ from injected insulin?

What inhaled insulin actually is

Inhaled insulin is real human insulin, delivered as a dry powder that you breathe in through a special inhaler, and it is designed mainly for meal-time sugar spikes (the rise after you eat).

It is not meant to cover your body’s basic insulin needs for the full day and night.

Key point:

If you have type 1 diabetes, inhaled insulin must be used along with a long-acting injection that provides background insulin. Without background insulin, type 1 diabetes can become unsafe quickly and the risk of ketones and ketoacidosis rises.

2. How it differs from injected insulin

Inhaled insulin (meal-time)

• Taken at the start of a meal (timing is closer to “at the meal” than many injected rapid‑acting insulins that are often advised 10-20 minutes before food).^[1,13]
• Works very fast and wears off faster than many injected meal insulins, so it mainly targets the meal rise and early post‑meal period.
• Useful when someone wants a needle-free option for the meal dose or finds pre‑meal injections difficult at work or in public.

Injected insulin

• Can be meal-time insulin (rapid‑acting or short‑acting) or all-day/night insulin (intermediate or long‑acting), depending on the type.
• Long-acting injected insulin is often essential in type 1 diabetes to provide basal coverage and prevent dangerous sugar and ketone problems.

3. Who can use inhaled insulin?

In the US, inhaled insulin is approved for adults with diabetes who need meal-time insulin (type 1 or type 2).

It can be considered if:

• You need insulin for meals and you want a needle-free option at meal-times.
• You can do the required lung testing and you do not have chronic lung disease.

4. Who should NOT use it.

Inhaled insulin can trigger sudden breathing spasm (bronchospasm) in people with certain lung conditions.

It is contraindicated in:

• Asthma.
• COPD (chronic obstructive pulmonary disease).

It also requires lung function screening as part of safe use.

Also, it is not for treating diabetic ketoacidosis (DKA).​

If someone is a current smoker or has recently stopped smoking, clinicians are usually very cautious because absorption, safety, and dosing become less predictable, and the label recommends avoiding use in active smokers and careful reassessment in recent ex‑smokers.

The “lung test” requirement.

Because it goes through the lungs, the standard recommendation in the prescribing information is:

• Do a breathing test (spirometry/FEV1) before starting.
• Repeat at 6 months.
• Then yearly thereafter while on therapy.

If lung function drops significantly, the doctor may stop it or switch back to injected insulin.

Common side effects patients notice

• Low sugar (hypoglycemia) can still happen, just like with any insulin, especially if the dose is too high or meals/physical activity are mismatched.
• Cough and throat irritation are relatively common because the insulin is inhaled as a powder through the mouth and into the lungs. 

7. A practical way to think about it.

If you struggle mainly with meal-time injections at work, inhaled insulin may help for that specific problem by letting you take your meal insulin quickly and discreetly at the table or in a break area.

But it usually means:

• You may still need at least one daily injection (background/basal insulin) if you have type 1 diabetes.
• You still need glucose monitoring (fingersticks or CGM), and you still need a clear sick-day and ketone plan just as with injected insulin.

Simple takeaway

Inhaled insulin can reduce needle use for meal doses, but it usually does not replace insulin injections completely, especially in type 1 diabetes. 

It is mainly a meal-time tool, and it requires lung safety checks and careful patient selection to be used safely.