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What Does Folic Acid 400 mcg Mean on a Label?
Folic acid 400 mcg is the amount behind the Reviralis Complete line that reads folate 680 mcg DFE. DFE is a conversion unit, so 400 mcg of folic acid prints as 680. The adult upper limit for folic acid from supplements is 1,000 mcg a day, and it can hide a B12 shortage.
Written by the Goreviralis label deskUpdated · 4 min read
Why does folic acid 400 mcg print as 680 mcg DFE?
DFE means dietary folate equivalents, a unit that corrects for how well the body absorbs each form. Folic acid in a supplement is absorbed better than folate in food, so 400 mcg of folic acid counts as 680 mcg DFE.
The label shows both: folate 680 mcg DFE (400 mcg folic acid), 170% of the Daily Value. The adult need is 400 mcg DFE a day, which is why two capsules sit above the target on paper (NIH ODS, Folate).
Do not read 680 as a larger dose of the vitamin. It is the same 400 mcg of folic acid in a different unit.
How close is 400 mcg to the 1,000 mcg upper limit?
It is 40% of the limit. The upper limit applies to folic acid from supplements and fortified foods, and it is 1,000 mcg a day for adults (NIH ODS, Folate).
| Measure | Amount | Note |
|---|---|---|
| Label, two capsules | 400 mcg folic acid | Prints as 680 mcg DFE |
| Adult need | 400 mcg DFE | From food and supplements |
| Upper limit | 1,000 mcg folic acid | Supplements and fortified foods |
| Room left | 600 mcg | Shared with every other product |
Fortified bread, cereal and pasta count toward that same ceiling. A second multivitamin with 400 mcg takes the total to 800 before breakfast cereal.
How can folic acid hide a vitamin B12 shortage?
Folic acid can fix the anemia that low B12 causes while the nerve side of the shortage keeps going unnoticed (NIH ODS, Folate).
That masking is the reason for the upper limit. People most likely to run low on B12 include older adults and people who eat no animal foods, so they are the ones to ask first. A blood test shows B12 directly, and a clinician orders it.
Folic acid may also interact with the seizure medicine phenytoin. The Reviralis label asks anyone with a history of seizures or on prescription medicine to check with a healthcare provider before use.
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See packsWhich medicines are worth checking against folic acid?
Seizure medicine comes first, then anything your pharmacist flags.
- Seizure medicine such as phenytoin: possible interaction with folic acid.
- Any prescription: the label asks you to check with a healthcare provider first.
- Other vitamins with folic acid: add the micrograms to the 400 on this label.
Ask: "Does folic acid change how my medicine works, and do I need a B12 check?" Keep taking prescribed medicine, including any antiviral, unless your prescriber says otherwise. No source we read tested Reviralis itself.
The other B vitamin amounts are on the supplement facts page. For the B6 side, read the B6 upper limit post, and see the side effects page for the wider list.
FAQ01
Folic acid questions
Is folic acid 400 mcg the same as 400 mcg DFE?
No. Folic acid in a supplement counts as 1.7 times its weight in DFE, so 400 mcg of folic acid equals 680 mcg DFE. The adult need is stated as 400 mcg DFE a day. The unit changes the number, not the dose swallowed.
What is the upper limit for folic acid?
For adults the upper limit is 1,000 mcg a day of folic acid from supplements and fortified foods. It does not apply to folate from natural food. The limit exists partly because folic acid can mask a B12 shortage.
Can folic acid hide low B12?
Yes. Folic acid can correct the anemia caused by low B12 while the nerve effects continue unnoticed. Anyone at risk of low B12, such as older adults, should ask a clinician about a blood test before taking folic acid regularly.
Does folic acid interact with phenytoin?
It may. The NIH fact sheet lists phenytoin as a medicine that folic acid may interact with. Anyone taking a seizure medicine should tell the prescriber about every supplement before starting one.
Does the label say anything about pregnancy and folic acid?
The Reviralis label asks pregnant or nursing women to check with a healthcare provider before use. Folic acid needs change in pregnancy, so a clinician should set the dose. We do not give a pregnancy dose.
Who wrote this02
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Pages built from the label, the sales page and linked NIH, CDC, FDA, FTC, Mayo Clinic and peer-reviewed sources.
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