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What to do if…
you develop a fever soon after starting an immune-suppressing medication and you are unsure how serious it is

Short answer

Treat this as urgent: call your prescribing team (including any out-of-hours advice line) or NHS 111 now and tell them you’ve started an immune-suppressing medicine and have a fever. If you feel very unwell, confused, breathless, have severe shivering, a rash that doesn’t fade when pressed, or you can’t stay awake, call 999 or go to A&E.

Do not do these things

  • Don’t “wait it out” overnight to see if it settles if you’re immunosuppressed — infections can escalate faster than usual.
  • Don’t take repeated doses of paracetamol/ibuprofen to keep the number down instead of getting medical advice (it can mask how unwell you are).
  • Don’t stop an immune-suppressing medicine suddenly unless a clinician tells you to (some need tapering, and stopping can cause harm).
  • Don’t rely on a walk-in/pharmacy visit as your main plan if you’re immunosuppressed with a fever — use your clinical team or NHS 111 so you can be triaged for urgent assessment.
  • Don’t drive yourself to A&E if you feel faint, confused, very weak, or shaky.

What to do now

  1. Check your temperature properly (now), and write it down.
    Use a digital thermometer if you have one. Note the time, the reading, and how you took it (mouth/ear/underarm). If you can, repeat once after ~15–30 minutes to confirm.
  2. Make the urgent call and use the right words.
    • If you have an “urgent advice” number for your specialist team (for example rheumatology/dermatology/gastroenterology/oncology/haematology/transplant), call that first (even out of hours).
    • Otherwise call NHS 111 and say: “I started an immune-suppressing medication on [date] and I now have a fever and feel unwell.”
      If you’ve been told you’re at risk of neutropenia/neutropenic sepsis, say that explicitly.
  3. If any danger signs are present, escalate immediately. Call 999 or go to A&E now.
    Go straight to emergency help if you have any of these: severe breathlessness, chest pain, new confusion, collapse/fainting, a new rash that doesn’t fade when pressed, lips/skin turning blue or very pale/mottled, severe rigors (uncontrollable shaking), very little urine, or you’re getting rapidly worse.
  4. Get your “information bundle” ready for the clinician (this speeds decisions).
    Put in one place: the medication name(s) and dose, when you started, any recent dose changes, any other immune-affecting meds (e.g., steroids), allergies, recent blood test results if you have them, and your latest temperature readings.
  5. Reduce avoidable risk while you’re arranging care.
    Keep warm and sip fluids if you can swallow safely. Avoid close contact with people at higher risk (for example older adults or anyone with serious health problems). If you need to attend A&E/urgent care, consider wearing a mask in crowded indoor areas.
  6. If you’re told to attend A&E/assessment, go now and say this at reception:
    “I’m on immune-suppressing medication and I have a fever — I need urgent assessment for possible serious infection.”
    If you’re on cancer treatment or have been warned about neutropenic sepsis, say that immediately.

What can wait

  • You do not need to figure out the exact cause of the fever right now.
  • You do not need to decide today whether to continue/stop the medication long-term — follow urgent clinical advice first.
  • You can postpone emailing work/sorting childcare until you’ve made contact with NHS 111/your clinical team and know whether you’re being seen.

Important reassurance

Feeling unsure is normal here. Immune-suppressing medicines can make infections harder to spot early and faster to worsen — seeking urgent triage is a sensible, protective step.

Scope note

This is first steps only. You may need tailored advice based on your specific medicine, diagnosis, and recent blood tests.

Important note

This is general information, not a diagnosis or a substitute for clinical care. If you are getting worse, feel unsafe, or can’t get prompt advice through your usual team, use NHS 111 or emergency services.

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