Welcome to NeuroTalk:

I'd like to expand on the B12 treatment and test results with you.
I strongly suggest you get the numbers of both your tests.
In the US, lab ranges are outdated, and "normal" is not really normal anymore. You should be at 400 US units or above to be considered low normal now.

The amount of B12 in a Bcomplex is very small. Many people cannot methylate (activate) the B12 in most vitamins which is cyanocobalamin. There are now inexpensive methylcobalamin tablets you can take. I'd recommend 5mg daily on an empty stomach, for 3 months. And then get retested. You should be at about 1000 for your serum reading by then.
Here is the medical site for doctors to explain the new (since 2003) treatment protocols:
http://www.aafp.org/afp/2003/0301/p979.html
If you were taking the supplements when you had your 2nd testing, that reading is not accurate and does not reflect what your status is without supplements.

There are people who follow the vegetarian diet and become low in B12. Also if you inherited the DNA error (present in about 10-30% of people) in activating B12 so it will work in the brain, and body properly, you cannot convert cyano in vitamins for yourself.

Methylcobalamin, the active form, is the cofactor for proper maintenance of sleep. It is necessary to convert serotonin to melatonin which is the sleep promoting hormone in your brain.
So if you don't have the methyl form in your brain, you will not sleep properly. All sorts of other neurological problems can result with low B12 in the brain.

Here is long and very detailed B12 thread here:
http://neurotalk.psychcentral.com/thread85103.html
It might be very useful for you to learn about this now, since you already tested low once for B12. It might mean you will need proper supplements for life, since you don't know why you were low to begin with.

Taking methylcobalamin daily correctly costs pennies a day. It is easy and the most inexpensive thing and corrects a very common problem in many Americans. You can find it online at iherb.com, Swanson's, Vitacost, or Puritan's Pride.