Q and A

Question

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?

Answer

Hi,

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.

40 comments

  1. Josh Peasegood

    Hi Irene, if possible it is best to wait to have your blood test. As everyone’s immune system works differently there is no defined amount of time you should wait. A cold can alter the results of a blood test and not give an accurate view of your overall health. If it is not possible to reschedule, having a blood test now can still be okay. But you will need to remind your doctor that your test was done when you had a cold. If the results appear too abnormal either from the cold or something actually going on, a second blood test will be ordered to confirm anyway.

  2. Irene

    Is it ok to get a blood test even if I have a cold . Or should I Waite ! If so how many days

  3. Josh Peasegood

    Hi Beatriz, yes you can. A fever may cause a temporary change in CD4 count but looking at CD4 percentage instead will give a more accurate result.

  4. Beatriz

    Hi my daughter has a fever and she needs to get blood work done can I still take her ?

  5. Simon Collins

    Hi Anne, sorry if this reply missed your appointment. The answer would have been to call the clinic. This is complicated because symptoms of a cold might be treated as symptoms of COVID-19.

  6. Anne

    I am scheduled for pre op blood work tomorrow
    I came down with a cold today
    Can I still get blood work done

  7. Josh Peasegood

    Hi Ann, did you have an injection for your vaccine? These shots cannot cause flu, rather you might experience some minor side effects for the next few days. CD4 count levels can be very variable even throughout the day. As long as you are feeling well enough, you should be okay to have your bloods taken. If the results are not as expected you can inquire about your CD4% as mentioned in the top question or opt for a repeat test.

  8. Ann

    I am on methotrexate injections and am due for my regular bliid test. But had flu injection last week and now have a bad dose of the flu. So im asking if nurses will still take my bloods or should i change the appointment thanks

  9. Simon Collins

    Hi Kate, are you also HIV positive? This is because the i-Base Q&A service is about HIV and related issues. In general, a cold is unlikely to affect blood tests for iron.

  10. Kate

    Will a common cold affect my blood test even just for checking iron levels?

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