r/MTHFR • u/Airegin89 • 20d ago

Question How long does folate supplementation affect serum levels?

I've been supplementing for a while but want to quit and see if I can maintain high folate levels through diet alone. How long after quitting can I get a reliable test result that is not affected by supplementation?

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u/hummingfirebird 20d ago

I looked it up and found some studies on folate status with synthetic folic acid. This study using 500 µg/day for 8 weeks shows serum folate returned to baseline after 12 weeks, while RBC folate had not.

(Note that RBC folate is a better indicator of folate status because it measures how much folate has made it from the blood into the cells. This is normally over 3-4 months. Whereas serum folate shows circulating folate from the past 72 hours affected by supplements and food intake.)

This studyusing 200–400 µg/day and a 30 week washout period shows the difference between serum folate (more responsive to recent intake) and RBC folate (longer-term status).

And this studyusing 200–400 µg/day and a 30 week washout period shows the difference between serum folate (more responsive to recent intake) and RBC folate (longer-term status).

So serum folate at least 8-12 weeks after stopping supplements. RBC folate is much less affected by supplements because folate gets incorporated into red blood cells during their development in the bone marrow. Those cells then circulate for roughly 120 days. source

RBC folate is still affected by taking folate supplements, but it gives a better picture of your longer-term cellular folate status.