Hello. This is an important question regarding your blood work.
In short: Yes, a head cold or cough can absolutely affect the accuracy of a
Ferritin test.
Ferritin is what we call an "acute-phase reactant." This means that when your body is fighting off an infection or inflammation-even a common cold-your Ferritin levels can spike significantly higher than they normally would.
Since your previous level was already elevated at 860, testing while you are sick may result in a "falsely high" reading that doesn't accurately reflect your body's true iron stores.
Recommendations
Postpone the Test: To get a truly accurate "baseline" reading, it is generally best to wait until you are fully recovered and symptom-free for at least 1–2 weeks.
Verify the Trend: Since your level is 860, your doctor is likely trying to determine if this is due to chronic inflammation, fatty
liver, or a condition like Hemochromatosis. Testing during a cold adds "noise" to the data that makes it harder for us to find the real cause.
Other Tests: If you are also having a Full Blood Count (FBC/CBC) done, the infection will likely show an increase in your white blood cell count as well.
Summary
While there is no harm in having the blood drawn, the results will likely be skewed. I suggest rescheduling the appointment for next week or once your cough has completely subsided to ensure the data is useful for your clinical management.
I hope you feel better soon and that your cough clears up quickly.