Shalynn, Yeah, 400 is on the low end and you can have symptoms at that level. Have you thought about getting some sublingual (under the tongue) B12? I like the Jarrow brand these days. iherb has very good pricing - I've been getting supplements from them for 10+ years.

When my ACh antibody tests were first done, my modulating antibody was 18 (with that same range of 0 - 20). Trends in tests are often as important as absolute numbers. Mine was above normal the next year (though I didn't find out until 7 years later cause the doctor didn't tell me about it or give me the results). According to some MG experts, there is a subset of MG patients who only have the modulating antibody (3-4% according to them).

Are you on any drugs that might interfere with the results, like Flovent, Advair or other steroids?

I hope you will start taking the sublingual B12. Since it's that low, you are probably not getting enough from your food. It takes about as long as you've had a low amount to heal. Remember that the body uses up B12 depending upon how much is needed. It's a fluid situation and those blood tests are only a static view of your B12.

I hope you can get other answers soon.

Annie