Diabetes and Aspergillosis: Infection Risk, Steroids and Blood Sugar

Person checking blood glucose at home while managing diabetes and aspergillosis — Keeping blood glucose within your agreed target range supports immune function and recovery during treatment.

Diabetes is common, and many people living with aspergillosis also have type 1 diabetes, type 2 diabetes or raised blood glucose caused by steroid treatment.

Having diabetes does not mean that you will develop aspergillosis, and most people with diabetes never do. However, diabetes can be one of several factors that affect how the body responds to infection and how treatment is managed. It is particularly relevant when it occurs alongside lung damage, poor nutrition, long-term steroid treatment or a serious illness.

Why can diabetes matter?

When blood glucose levels are frequently above their usual target range, the body may not fight infections as effectively. High glucose can affect the function of some immune cells and may make recovery from infection more difficult.

For aspergillosis, diabetes is usually one part of the picture, rather than the sole explanation. Other important factors may include:

previous tuberculosis or another lung infection that has left cavities or scarring;
bronchiectasis, COPD, sarcoidosis or another long-term lung condition;
long-term or repeated corticosteroid treatment;
low body weight, poor appetite or malnutrition;
serious viral illness, hospital admission or intensive care treatment; and
medicines or conditions that suppress the immune system.

In other words, risk can “stack up”. Diabetes may add to the effect of existing lung disease or treatment, but it does not make aspergillosis inevitable.

Does high blood sugar “feed” Aspergillus?

Not in the simple sense that sugar in the bloodstream directly feeds fungus in the lungs. Blood glucose and the airways are separated by several protective barriers.

There is a small amount of glucose in the thin fluid lining the airways, and persistently high blood glucose can alter that environment. However, the strongest evidence that this directly encourages growth is for some bacteria, not for Aspergillus specifically.

The more important reason that glucose control matters is the immune system. Persistently high blood glucose can affect how immune cells recognise, reach and destroy germs, including fungi. It may therefore make infections harder to control or recovery slower.

The practical message is not to blame yourself for a high reading or to try to manage an infection through diet alone. Keeping glucose within the range agreed with your diabetes team supports your immune system and recovery, alongside the right respiratory and antifungal treatment.

Diabetes and chronic pulmonary aspergillosis

Chronic pulmonary aspergillosis (CPA) usually develops in lungs that have already been damaged. Diabetes is recognised as one factor that may increase vulnerability, especially in people with previous tuberculosis, weight loss or poor nutritional status.

A recent study in people being treated for pulmonary tuberculosis found that diabetes and low body weight were both associated with a higher likelihood of CPA. This is useful evidence, but it does not mean that every person with diabetes requires tests for aspergillosis. Testing is guided by the whole clinical picture: symptoms, previous lung disease, scans, blood tests and sputum results.

Speak to a healthcare professional if you have diabetes and develop persistent or worsening respiratory symptoms, particularly if you also have a history of significant lung disease.

Steroids: an important practical issue

Corticosteroids are an important treatment for many people with asthma and ABPA. They can reduce harmful inflammation and, in some situations, are essential. However, steroid tablets and injections can raise blood glucose levels. They may make existing diabetes harder to manage or occasionally trigger steroid-induced diabetes.

This does not mean that you should avoid, reduce or stop steroids on your own. Suddenly stopping steroid treatment can be dangerous. Instead, make sure the clinician prescribing steroids knows that you have diabetes or have previously had high blood glucose.

Your diabetes team, GP or specialist team may recommend temporary changes to glucose monitoring or diabetes medication while you are taking steroids. The right plan is individual and may change when the steroid dose is reduced.

What about inhaled steroids?

Inhaled corticosteroids generally have less effect on blood glucose than high-dose steroid tablets or injections, but some people may still notice a change, particularly at higher doses. Continue your inhalers as prescribed and discuss concerns with your usual healthcare team rather than stopping treatment.

Looking after both conditions

Good diabetes care supports your overall health while you are being treated for aspergillosis. Useful steps include:

attending diabetes reviews and monitoring blood glucose as your team has advised;
telling your diabetes team about new steroid treatment, significant infection or a hospital admission;
telling your aspergillosis or respiratory team about diabetes medicines and any major changes to them;
keeping regular meals and fluids going as far as possible when you are unwell;
asking for dietary support if poor appetite, weight loss or nausea are making it difficult to eat enough; and
keeping vaccinations up to date where they are recommended for you.

Antifungal medicines can interact with many other treatments. Bring an up-to-date list of all medicines, including diabetes medicines, to appointments and ask a pharmacist or prescriber to check for interactions whenever something changes.

When you are unwell

Infections can raise blood glucose levels, even if you are eating less than usual. If you have diabetes, follow the sick-day guidance given by your diabetes team. This may include checking glucose more often and, for some people, checking ketones.

Contact your diabetes team, GP, NHS 111 or your usual urgent-care route if you are unable to keep fluids down, have repeatedly high or low readings outside the range your team has advised, have ketones, or are becoming increasingly unwell.

If you have symptoms that might suggest worsening lung disease — such as a persistent increase in cough, breathlessness, fever, weight loss, new chest pain or coughing up blood — contact the team managing your respiratory condition. Significant coughing up of blood requires urgent medical assessment.

Key messages

Diabetes is common and most people with diabetes do not develop aspergillosis.
It can contribute to risk when combined with lung damage, poor nutrition, steroid treatment or severe illness.
High blood glucose does not simply “feed” Aspergillus in the lungs; its more important effect is on immune function and recovery.
Steroids can raise blood glucose, so diabetes management may need temporary adjustment during treatment for ABPA or another condition.
Do not stop steroids, antifungals or diabetes medicines without medical advice.
Good communication between your diabetes, respiratory and pharmacy teams helps keep treatment safe.