Are they timed release? If so I don't think they will work well.
500mcg is the lowest dose recommended..very borderline.

I'd take 4 to start (1mg) on an empty stomach. I assume they are cyanocobalamin?

The methylcobalamin is not commonly available in stores but you can find it here:

http://www.iherb.com/Search.aspx?kw=methylcobalamin
The Jarrow brand is good, and very inexpensive.

245 is too low.
Here is a site to read: (they use 400 as a cut off)
Japan uses 500 as a cut off value:
http://www.aafp.org/afp/20030301/979.html

Much of the problem is the lab reporting. Doctors rarely question labs...and the ranges in US are low. Your doctor is just typical. You can print out the AAFP article and take it to him! Doctors have therapeutic books that they use for a guide, and it takes eons for them to be republished with new
articles (they are very expensive too). Unless a drug salesman tells them stuff, many doctors do not look for information themselves! States force CME education for relicensure, but if this topic is not offered, then no dice! Even Dr. Latov's book has two huge typo errors about B12 in it! Sad but true!

If people are low in B12 one has to assume that normal absorption from food is impaired/broken, and then you have to rely on "passive" absorption which requires very high oral doses.