The new recommended lowest normal in US is 400.

That test was almost 2 yrs ago! Tests are only a snapshot in time. If you were coming down, or living off your stored B12 in the liver then, today your result may be lower.

So getting a new test might reveal something.

We at the PN forum try to keep our levels at least at 1000 and some do more.

B12 is not the only nutrient people can be low with. Low D also causes problems. That should be tested as well.

Low magnesium can cause all sorts of sensations, including twitching.

If you were taking something last test, I'd still take it this time around, to see under the same circumstances if anything has changed. Not all B12 is absorbed orally, especially if you take it with food. Taking on an empty stomach is best.

Do you take acid blocking drugs? Zantac or Prilosec etc?
These drugs impair many things in the body:
B12
folate
calcium
magnesium
zinc
iron.

There are people who cannot methylate B12 or folic acid. These will test as present in the blood, but since they are not activated do not work for you. The test is MTHFR DNA test, and it is a genetic failure in 10-30% of US adults. If you have this genetic polymorphism you cannot methylate (activate) B12 and folic acid and you would still have symptoms of deficiency with both.

Consuming a diet high in sugar, and/or starchy carbs can lead to low blood sugars (a crash of sorts), and this can present with twitching and other sensations when blood sugar is low. If you feel better when you eat, that is a sign of possible impaired glucose utilization, or pre-diabetes.