[8][9] The inhaled form is used in the long-term management of asthma and chronic obstructive pulmonary disease (COPD).

[13][14][15] Common side effects with the inhaled form include respiratory infections, cough, and headaches.

[16] Common side effects with the pills include feeling tired, vomiting, and joint pains.

[16] Serious side effects include an increased risk of infection, loss of bone strength, and cataracts.

[22][23] Budesonide is given by metered-dose inhaler or nebulizer for maintenance and prophylactic treatment of asthma, including patients who require oral corticosteroids and those who may benefit from a systemic dose reduction.

[24] Formulations of delayed-release budesonide are an effective treatment for mild-to-moderately active Crohn's disease involving the ileum and/or ascending colon.

[34][35] These include nose irritation or burning, bleeding or sores in the nose, lightheadedness, upset stomach, cough, hoarseness, dry mouth, rash, sore throat, bad taste in mouth, change in mucus, and blurred vision.

[36] Other symptoms which should be reported immediately include difficulty in breathing, swelling of the face, white patches in the throat, mouth, or nose, irregular menstrual periods, severe acne, and on rare occasions, behavioral changes (mostly affecting children).

[37] Symptoms of an overdose include more specific symptoms such as darkening and thinning of the skin, changes in body fat around the face, neck, back, and waist, increased acne or facial hair, menstrual problems, impotence, or loss of interest in sex, as well as some less specific symptoms such as diarrhea, dizziness, loss of appetite, mental depression, nausea, skin rash, unusual tiredness or weakness, or vomiting.

[48] A high fat meal when taken with the capsule can lengthen the time it takes to reach Cmax by another 2.3 hours, but will not have any other affects on the pharmacokinetics properties of budesonide.

[49][48] Budesonide is 80-90% metabolized at first pass in the liver by the hepatocytic cytochrome P450 isoenzyme 3A4 (CYP3A4) into two metabolites: 16 alpha-hydroxyprednisolone and 6 beta-hydroxybudesonide.

[63] After a University of Oxford research team found in a trial with 1,700 patients that budesonide could benefit many people over 50 with COVID-19 symptoms, it was recommended from 12 April 2021, by the National Health Service in the UK for general practitioners (GPs) to treat COVID-19 on a case-by-case basis.