Blog of Bloodworks Northwest

Tips to pass the iron test (hematocrit)

The finger prick to test iron levels, called a hematocrit (hematocrit is the percentage of red blood cells in your blood), is a necessary evil: we need to make sure that you have enough iron in your blood to safely take a pint of it.

There are few things more disappointing for blood donors then making time to give and then not being able to do so when they don’t pass the hematocrit, particularly during the holiday season when the blood supply gets low.

Sophie, a phlebotomist at our First Hill location in Seattle, has the following tips to ensure that you can keep saving lives every 56 days.

Increase your circulation

mittensLow blood circulation in the hand can cause the hematocrit to give an artificially low reading, even if your iron levels are actually within the acceptable range. Less blood flow = lower readings. This is a problem we see more of when it’s chilly outside.

To improve circulation, keep your hands warm when arriving to their blood center or mobile donation site and run your hands under warm water after filling out the questionnaire.

Add iron-rich foods to your diet

spinachWhile running your finger under warm water increases blood flow, increasing your circulation does nothing to help you pass the test if you just don’t have the iron to begin with; make sure that you keep your iron levels within the acceptable range. Even longtime donors may come in to find that suddenly their iron levels aren’t high enough; this happens to both men and women, and is fairly common: on an average day, approximately one out of ten donors is deferred because of a low iron count.

Increase your consumption of iron rich foods, such as red meat and dark leafy greens, starting up to a week prior to donating. You can also talk to your doctor about taking an iron supplement; we do not recommend adding this to your diet without consulting a physician first.

A low iron count also doesn’t mean that you are anemic. It’s only if you are at or below 31.5 hematocrit that we recommend that you talk to your doctor — anywhere in the 31.8 – 37.2 hematocrit range is normal but just doesn’t meet our standards.

Come back again

clock6Iron fluctuates on a daily basis. Even if your iron levels are too low to meet our standards on a given donation, you might be okay for the next one. You can donate three days after being deferred for low iron, so come back as soon as you are eligible again.



December 9, 2013 10:43AM
  • Jamie DeVriend

    Thank you for posting this advice. I think for anyone donating blood out there, preparing in advance to pass the hematocrit will go a long way to assuring one isn’t disappointed when they arrive. It also didn’t occur to me to keep the hands warm before arriving, but it makes sense.

  • Ken

    Is there any way I could get the hematocrit test BEFORE filling out the questionnaire? I’ve been donating for over 30 years, and only failed the Hemoglobin test once. But now that you do a Hematocrit test instead, I’ve failed it three times in a row. It makes me reluctant to even try.

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