Blood trialling while sick beside a disorientation?

I had to pilfer a blood test beside a fever yesterday for a charge application, and the doctor said that it wouldn't affect the results of whether i was fine or not. Is this true?Blood trialling while sick beside a disorientation?
If this was of late a viral infection and not a chronic infection, it should not matter.
It depends what the blood interview was for. Your white blood cell count would be difficult because of your illness