Iron supplement's affect on ferritin lab

[deniseross]

I just read here that I should stop iron supplements prior to having ferritin tested? I just took some iron this morning and am scheduled to have a bunch of lab tests run tomorrow. How will this affect the test?

[SlowDragon Administrator]

Probably

Ideally you should stop iron supplements a week before testing iron and ferritin levels

And avoid iron rich food night before test …..so no large steak the night before testing

[humanbean]

The length of time that iron supplements might possibly alter results on any iron-related blood tests tends to differ depending on source.

A few years ago there was advice on the web suggesting that the gap from last dose of an iron supplement to getting blood taken should be a week. For example :

healthboards.com/boards/ane...

The link above suggests that the gap isn't so necessary for a ferritin (iron stores) test, but I can't see why ferritin would be a special case when serum iron and other iron-related tests need a week's gap.

Another link - this time about leaving a week's gap before a colonoscopy :

bupa.co.uk/health-informati...

Nowadays the advice tends to be less draconian - this is what labtestsonline has to say :

Test Preparation Needed?

Your doctor may request that you fast for 12 hours prior to some iron blood tests. In this case, only water is permitted. You should not take any iron tablets for 24 hours before the test. Iron is absorbed rapidly from food or tablets, and can make your blood iron levels falsely high.

Source : labtestsonline.org.uk/tests...

Personally, I always stick to a week. But if you do go ahead with a shorter gap then it would be worth keeping a note of how long the gap was between last dose and blood draw. It may help you to explain your results when you have more results in future to compare with. It may turn out that your test tomorrow might look surprisingly good when compared to another test in 2 - 3 months.

I would definitely suggest fasting for 12 hours before the blood draw.

[deniseross in reply to humanbean]

Oh, dear, I did not know about the fasting... I may have to change the time now. Thank you for the heads up!

[humanbean in reply to deniseross]

If you want to see more opinions you should search for "how long to stop iron before testing".