You need to take B12 on an empty stomach. It won't be absorbed with or after food.

Without knowing WHY you are so low, one has to wonder if you have
1) inherited pernicious anemia or autoimmune damage to the parietal cells of the stomach?

2) or, taking acid blocking drugs every day, or metformin?

3) or having the MTHFR mutation which is becoming fairly common (up to 40% predicted to have this).

4) malabsorption due to inflamed intestines (Crohn's disease) or
gluten intolerance.

With #3, you would need activated B12, called methylcobalamin.
And activated folate, called methylfolin. (Metafolin)
People with the mutation cannot activate cyanocobalamin in the tissues, so it is useless.

So cut to the chase and use the inexpensive Methylcobalamin.
I'd do 5mg on an empty stomach 1 hr before breakfast daily.

This should raise you up within 3 months to about 1000pg/ml

500mcg a day is very low and one study that measured absorption found only about 9 mcg were absorbed.
This is the table published in the study:

http://www.ncbi.nlm.nih.gov/pmc/arti...able/T1/#TF1-4

Taking orally most approximates how B12 is absorbed and utilized from food.

You can do the injections if you choose, but they are invasive and expensive and use the old cyano form, mostly.

You can buy methylcobalamin now at Costco and Walgreen's.
And online at various places. iherb.com or Swanson's, etc.
iherb also has the MetaFolin. iherb is a discount high quality supplier that carries all sorts of brand name products at substantial discount. For many years it was one of the few online sources for methylcobalamin. Now the B12 topic is more disseminated and so other places now carry it too.

Thank you mrsD for your detailed reply. However, how can I find out which of the above causes are responsible for my low B12 levels?

Also, I am complete vegetarian (from India) and my brother and both sisters have found to have low B-12 levels in their test. Can it be hereditary?

The vegan lifestyle will contribute quite a bit.

Now that the methyl forms (activated) of both folic acid and B12 are available and inexpensive, there is no reason to use cyano at all.

There is quite a bit of research coming out of India on this subject...in fact before the research here in US... because of the vegan lifestyle.

One can only get B12 from animal sourced foods. Veggies do not supply it.

If you search Google you will find articles like this...using keywords --B12 deficiency India---

http://articles.timesofindia.indiati...cts-deficiency

Hello,

I just learned that my B12 levels are low at 394, so I will get shots temporarily to get my levels up higher to see if I feel better. My vitamin D levels were only 41 so I will keep taking my supplement for that.

My mom had B12 deficiency and had to take shots later in life. I also have off levels for my thyroid but I don't know how to read the test results for that. I think if my B12 was as low as yours I would definitely take the shots for awhile to increase your levels faster. Good luck!