Is asthma linked to diabetes? Studies find an association between asthma and type 2 diabetes, but they do not show that one causes the other. A 2025 register study in Thorax of 5,299,245 Swedish adults found the odds of type 2 diabetes were 1.47 times higher in people with asthma than in people without it. Researchers also found that part of the link comes from shared family factors, and a 2025 review says type 2 diabetes goes with worse asthma outcomes. Steroid medicines for asthma are a separate question: a retrospective analysis of inhaled budesonide trials found no increase in new diabetes, while the review says steroids taken as tablets or injections for flare-ups can worsen blood sugar control.
Key takeaways
- In the Swedish study, the link between asthma and type 2 diabetes was stronger in women than in men and remained after adjusting for body mass index (BMI). A sibling analysis suggested the link is partly due to shared family genetic and environmental factors. The study cannot show which condition came first.
- A 2025 review says type 2 diabetes is present in up to 16% of people with asthma and is associated with more flare-ups, more hospital stays, and a lower FEV1/FVC ratio. It also says controlled studies in people are limited.
- Steroid tablets or injections given for asthma flare-ups can raise blood sugar, according to the review. Studies of inhaled budesonide did not find new diabetes or a significant rise in fasting blood sugar.
- The Centers for Disease Control and Prevention (CDC) says to take asthma medicine exactly as your doctor tells you. Controller medicines help you have fewer and milder asthma attacks, so blood sugar worries are a reason to call your prescriber, not to stop.
- Trouble breathing that comes on suddenly or interferes with talking needs a call to 911.
Asthma and Diabetes: The Short Answer
- There is an association. People with asthma are more likely to have type 2 diabetes in large population studies.
- The direction is unclear. Studies of this kind cannot show whether asthma, diabetes, or shared factors come first.
- Diabetes may make asthma harder to control. Reviews report more flare-ups and hospital stays when type 2 diabetes is present.
- Medicine type matters. Steroid tablets and injections can raise blood sugar. Inhaled steroids did not in the studies below.
- Do not stop an asthma medicine on your own. Ask your prescriber and pharmacist how your medicines fit together.
What Asthma Is
CDC says asthma is a disease that affects the lungs and causes wheezing, breathlessness, chest tightness, and coughing at night or early in the morning. If you have asthma, you have it all the time, but you have asthma attacks only when something bothers your lungs. During an attack, the sides of the airways swell and shrink, less air gets in and out, and mucus can clog the airways. A doctor may use a breathing test called spirometry, which measures how much air you breathe out after a very deep breath, before and after you use asthma medicine.
What the Studies Found
| Study | Who was studied | What it found | Limits |
|---|---|---|---|
| Mubanga and colleagues, 2025, Thorax | 5,299,245 Swedish adults in national registers | Asthma and type 2 diabetes were linked (odds ratio 1.47, 95% confidence interval 1.45 to 1.49; 1.30 in men and 1.63 in women). In a subset with BMI data, odds ratios of 1.51 in men and 2.04 in women fell to 1.45 and 1.76 after adjusting for BMI. Diabetes was also somewhat more likely when a full sibling had asthma (odds ratio 1.13) | Cross-sectional, so it cannot show which came first. BMI alone did not explain the link |
| Pham, Corcoran, and Foer, 2025, Current Opinion in Allergy and Clinical Immunology | Review of published research | Type 2 diabetes in up to 16% of people with asthma. Type 2 diabetes was associated with more exacerbations, more hospital stays, and a lower FEV1/FVC ratio | The authors say prospective, controlled human studies are limited |
| Rogala and colleagues, 2020, Journal of Asthma | 2,431 adults sorted into asthma only, asthma with diabetes, and diabetes only | Average HbA1c was 7.23% with both conditions and 7.42% with diabetes only, not a significant difference. Diabetes control criteria were met in 48.5% and 50.6%. Severe asthma was linked to poorer diabetes control | Cross-sectional |
| O'Byrne and colleagues, 2012, Respiratory Medicine | Retrospective analysis of double-blind trials of budesonide in asthma (26 trials) or COPD (8 trials) | New-onset diabetes or high blood sugar was reported in 0.13% on budesonide and 0.13% on placebo in the asthma trials (hazard ratio 0.98). In COPD it was 1.3% and 1.2% (hazard ratio 0.99) | One drug's trials, analyzed after the fact, and not trials built to answer this question |
The Swedish team described the link as partly shared family genetic and environmental factors. Excess weight is one shared factor, but BMI alone did not explain the link there. Because these are association studies, they do not tell you that having asthma will lead to diabetes, or the reverse. O'Byrne's team ran its analysis because an earlier case-control study had reported a higher diabetes risk with inhaled steroids, so findings differ between study types.
Steroid Medicines: Two Different Questions
Steroid medicines for asthma come in different forms, and the sources treat them differently.
| Form | What the sources say about blood sugar | What to do |
|---|---|---|
| Steroid tablets or injections for a flare-up | The 2025 review says systemic steroids used for asthma exacerbations worsen glycemic control. CDC lists corticosteroids among the medicines that can contribute to diabetic ketoacidosis | Tell your diabetes team when one is prescribed, and ask what to check and when. Our guide covers whether prednisone raises blood sugar |
| Inhaled steroids used every day as a controller | In budesonide trials analyzed together, new-onset diabetes was reported at the same rate as on placebo, and a retrospective analysis cited in the review found no significant new high blood sugar or diabetes. In Rogala's study, budesonide up to 825 micrograms a day had no significant effect on fasting glucose | Keep taking it as prescribed. Ask your prescriber about any change |
| Other medicines you take | Many medicines can raise blood sugar | Our list of medicines that raise blood sugar is a starting point for a pharmacist conversation |
These are findings from studies. They are not dosing advice, and the right medicine and dose for your asthma is your prescriber's decision. CDC says asthma medicines can have side effects, most of them mild, and to ask your doctor about the side effects of yours.
If You Have Both Conditions
Rogala's study found that severe asthma went with poorer diabetes control, and the review links type 2 diabetes with worse asthma outcomes. In practice, that means both teams benefit from knowing about both conditions. CDC says you can control asthma by knowing the warning signs of an attack, staying away from triggers, and following your doctor's advice. It also says that if you need your reliever medicine more and more, you should visit your doctor to see whether you need a different medicine.
Asthma is also one of the risk factors CDC lists for chronic obstructive pulmonary disease (COPD), and CDC lists diabetes among conditions people with COPD are more likely to have. Our guide on COPD and diabetes covers that link. For the wider picture, see how diabetes affects the lungs.
Breathing Trouble: When to Get Help
MedlinePlus says to go to the emergency room or call the local emergency number if breathing difficulty comes on suddenly or seriously interferes with breathing and even talking, or if someone stops breathing. The American Lung Association says an asthma flare-up is one cause of sudden shortness of breath, and that breathlessness with chest pain or pressure, fainting, or nausea is a medical emergency. Our guide on diabetes and shortness of breath lists other causes, including diabetic ketoacidosis, which CDC says needs emergency care when someone has fast, deep breathing, fruity-smelling breath, or trouble breathing.
Questions to Ask Your Care Team
- Have I needed steroid tablets or injections for asthma in the past year, and did my blood sugar change?
- If I am prescribed a steroid course, what should I check, and when should I call?
- Do any of my asthma medicines, or my other medicines, affect blood sugar?
- Is my asthma well controlled, and would my diabetes team and asthma clinician benefit from sharing notes?
- Which breathing symptoms should send me to urgent care?
Frequently Asked Questions
Does asthma cause diabetes?
Studies link the two, but they do not show that asthma causes diabetes. In a Swedish register study of more than 5 million adults, asthma and type 2 diabetes were associated, and a sibling analysis suggested shared family factors. The study could not show which condition came first.
Does diabetes make asthma worse?
A 2025 review reports that type 2 diabetes is associated with more asthma flare-ups, more hospital stays, and a lower FEV1/FVC ratio. The authors say prospective, controlled human studies are limited, so this is an association and not proof of cause.
Do inhaled steroids cause diabetes?
A retrospective analysis of budesonide trials found new-onset diabetes or high blood sugar was reported at the same rate as on placebo, and another study found no significant effect of budesonide up to 825 micrograms a day on fasting glucose. An earlier case-control study had reported a higher risk, so results differ by study type. These are study findings and not advice, so ask your prescriber about your own medicine.
Can steroid tablets for an asthma flare-up raise blood sugar?
Yes. The 2025 review says systemic steroids used for asthma flare-ups worsen glycemic control. Tell your diabetes team when a steroid course is prescribed, and ask what to check and when.
Should I stop my asthma medicine if my blood sugar is high?
No. CDC says to take asthma medicine exactly as your doctor tells you, and that controller medicines help you have fewer and milder attacks. If you are worried about blood sugar, call your prescriber or pharmacist before changing anything.
Is the link different for women and men?
In the Swedish study, the association was stronger in women than in men. The overall odds ratio was 1.63 in women and 1.30 in men, and in a subset with BMI data it stayed at 1.76 in women and 1.45 in men after adjusting for BMI. The study does not explain why.
References
- Mubanga M, Gong T, Smew AI, et al. "Association between asthma and type 2 diabetes in a Swedish adult population: a register-based cross-sectional study." Thorax. 2025;80(6). Accessed November 2026.
- Pham A, Corcoran R, Foer D. "The role of type 2 diabetes in the severity of adult asthma." Current Opinion in Allergy and Clinical Immunology. 2025;25(1):34–40. Accessed November 2026.
- Rogala B, Bożek A, Gluck J. "Is there a relationship between asthma and diabetes?" Journal of Asthma. 2020;57(12):1332–1338. Accessed November 2026.
- O'Byrne PM, Rennard S, Gerstein H, et al. "Risk of new onset diabetes mellitus in patients with asthma or COPD taking inhaled corticosteroids." Respiratory Medicine. 2012;106(11):1487–1493. Accessed November 2026.
- Centers for Disease Control and Prevention. "About Asthma." Accessed November 2026.
- Centers for Disease Control and Prevention. "Diabetic Ketoacidosis." Accessed November 2026.
- Centers for Disease Control and Prevention. "About COPD." Accessed November 2026.
- MedlinePlus. "Breathing difficulty." Medical Encyclopedia. Accessed November 2026.
- American Lung Association. "Shortness of Breath: Causes, Warning Signs & When to Seek Help." Accessed November 2026.
Next Steps
If you have asthma and diabetes, bring both medicine lists to your next visit and ask whether any steroid course is coming up. Keep taking your asthma controller medicine as prescribed, and call 911 for sudden or severe trouble breathing.
For adults with type 2 diabetes or prediabetes who want lifestyle education alongside clinical care, the Done With Diabetes™ program, a lifestyle education protocol, organizes learning about meals, movement, sleep, and stress. It does not diagnose or treat asthma or diabetes, interpret symptoms or test results, change medicines, or replace your care team.