Q and A


How long should I wait after a cold before getting my blood test?

I have a cold/slight touch of the flu and I was due for my blood tests today, however I have reschedule them until next week. My question is: how long does it take for your CD4 to go back my normal range… How long should I wait after a cold before getting my blood test?



Thanks for your question.

Your CD4 count and viral load can be affected by other viruses, such as the flu. It is possible therefore that your test results might be affected by your recent infection. Unfortunately as everyone has a unique immune system, the time it takes to recover from a cold or flu will vary and this may be reflected in your test results. It’s also worth noting that a cold will likely have less of an effect than definite flu (influenza).

As this may be hard to predict, you can ask the doctor to check CD4 percentage as well as your CD4 count. Follow this link for more information about CD4%.

It’s also possible that your viral load could blip above undetectable because of an infection. If your viral load has increased you should have another test to check the result. This means you may be better off going for your tests as planned and rescheduling them again if anything looks out of the ordinary. You can also give your clinic a call beforehand and ask if they have any recommendations for rescheduling.


  1. Josh Peasegood

    Hi Grace, yes. Your results are still reliable. It is good that they remained normal while you had a cold – it means your infection did not cause too much trouble.

  2. Grace

    I was starting to come down with a cold on a Monday when I had a full blood count blood test, the results came back normal – are they still reliable even if I had a slight sore throat?

  3. Simon Collins

    Hi Glen, are you HIV positive as you don’t mention this? If yes, then colds are not listed on this NHS page about health conditions that can affect blood pressure (BP).

    This page does say that some remedies for cold can affect BP though.

  4. Glen

    Does a cold affect my blood pressure?

  5. Josh Peasegood

    Hi Colleen, yes you can. If there are abnormal results the blood count can be repeated but a cold should not prevent you having this test.

  6. Colleen

    Can I have a full blood count done if I have a cold

  7. Josh Peasegood

    Hi Ally, yes it is okay to go ahead with your blood test. The tests you have mentioned are unlikely to be significantly effected by having a cold, if at all. Should a result appear skewed, a second test can always be done to ensure the result is accurate. But having a cold should not cause you to postpone this test.

  8. Ally

    I am meant to be having blood tests done for the following ….B12,BC,Bone,CRP,E,FOL,VITD and myeloma screen-Electrophoresis blood but i have got a cold (bunged nose/sore throat)will this affect my results?should i wait or go ahead?


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