Iron (Fe) Test

Come in the morning, and fasting is preferred. Serum iron follows a daily rhythm and is normally at its highest early in the day, which is what the reference range assumes, so an afternoon sample can read differently for no meaningful reason.

It matters a great deal, and it is the single most common reason for a confusing iron result. A tablet taken that morning can push the blood level up sharply for hours, so the test measures the tablet rather than your actual iron status. Ask your doctor how long to pause before testing, and tell the nurse when you last took one.

Not really, and this is worth knowing before you book. Serum iron shows how much is circulating at that moment, which moves through the day and with what you have eaten. Ferritin shows how much your body has in store, which is the more stable and more useful number. Most doctors read iron together with ferritin and iron binding capacity rather than any one of them alone.

It might be, and it is one of the common causes, particularly in women with heavy periods. But persistent tiredness has many causes, including thyroid problems, vitamin B12 deficiency and poor sleep, and iron studies answer only one of them. If tiredness is the reason you are here, see your doctor so the right group of tests is chosen rather than one at a time.