Why Does a Steroid Injection Affect the Immune System?
Corticosteroids reduce inflammation by decreasing the activity of certain immune cells and inflammatory chemicals. While this helps relieve pain, swelling, and stiffness, it can also temporarily reduce the body’s immune response.
This effect is one of the reasons steroid injections are effective for treating conditions such as:
- Osteoarthritis
- Frozen shoulder
- Bursitis
- Tendonitis
- Plantar fasciitis
- Tennis elbow
- Trigger finger
The degree of immune suppression varies depending on the type of steroid used, the dose injected, and individual patient factors.
How Long Does the Immune Suppression Last?
The exact duration of immune suppression varies depending on the type of corticosteroid, dose, injection site, and your overall health. However, research suggests the immune response follows a general timeline:
| Time After Steroid Injection | What Happens? | Immune System Effect |
|---|---|---|
| 0–24 hours | The corticosteroid begins reducing inflammation at the injection site. | Minimal systemic immune suppression. |
| 24–72 hours | The steroid reaches its greatest anti-inflammatory effect. | Highest level of temporary immune suppression, although it is usually mild after a single injection. |
| 1–2 weeks | Pain relief often continues as inflammation decreases. | Mild immune suppression may still be present but gradually begins to lessen. |
| 2–4 weeks | The steroid’s effects continue to wear off. | The immune system typically returns to its normal function in most healthy adults. |
| Beyond 4 weeks | The medication has largely been cleared from the body. | No ongoing immune suppression is expected from a single corticosteroid injection. |
Who Is More Likely to Be Affected?
The temporary impact on the immune system may be more relevant if you:
- Have diabetes.
- Have a weakened immune system.
- Take immunosuppressive medications.
- Are undergoing cancer treatment.
- Have an active infection.
- Are planning surgery or vaccination.
In these situations, your clinician may discuss the timing of the injection and whether alternative treatments should be considered. To learn more about the side effects of cortisone injection, read our blog here.
This article is intended for informational purposes only and should not replace professional medical advice. If you are experiencing persistent symptoms, please consult a qualified clinician.
Frequently Asked Questions
Does a steroid injection weaken your immune system?
Yes. A corticosteroid injection can temporarily suppress parts of the immune system, but the effect is usually mild and short-lived after a single injection.
How long does immune suppression last after a steroid injection?
For most people, immune suppression is greatest during the first 24–72 hours and generally returns to normal within 2–4 weeks.
Can I catch an infection more easily after a steroid injection?
The risk is slightly increased for a short period, but serious infections are uncommon in healthy individuals. Practising good hygiene can help reduce the risk.
Can I have a steroid injection if I'm unwell?
Steroid injections are usually postponed if you have an active infection. Speak to your clinician before treatment if you’re feeling unwell