About all aspects of vitamin B12 you received many articles from me over the past years.
The blood examination of B12 is not giving much information in it self.It can be normal or even high and there still may be a serious problem.
A low value  does give a clue of what is going on.
I hope to explain this once more in depth.
Other more appropriate examinations are at the moment still not done as a routine in laboratories.[methylmalonic acid etc].As you know I advise in all case of doubt to receive injections and not tablets. 
Remarkable  over the years I have been telling patients that-with a low level of B12,increasing the amount of meat eaten probably  will not help.
Interesting-in this connection -to see the article below.
I was not aware of the fact that milk and fish could be such a relative important source.[that the B12 of these sources are seemingly much better absorbed]

From the article:..................Plasma vitamin B-12 was associated with intakes of increasing amounts of vitamin B-12 from dairy products or fish (P for trend <0.001 for both) but not with intakes of vitamin B-12 from meat or eggs.

Am J Clin Nutr (February 3, 2009). doi:10.3945/ajcn.2008.26598

© 2009 American Society for Clinical Nutrition 


Dietary sources of vitamin B-12 and their association with plasma vitamin B-12 concentrations in the general population: the Hordaland Homocysteine Study1,2,3
Anna Vogiatzoglou, A David Smith, Eha Nurk, Paula Berstad, Christian A Drevon, Per M Ueland, Stein E Vollset, Grethe S Tell and Helga Refsum

1 From OPTIMA, the Department of Physiology, Anatomy & Genetics, University of Oxford, Oxford, United Kingdom (AV, ADS, and HR); the Department of Nutrition, Institute of Basic Medical Sciences, Faculty of Medicine, University of Oslo, Oslo, Norway (AV, EN, PB, CAD, and HR); the Section for Pharmacology, Institute of Medicine, University of Bergen and Haukeland Hospital, Bergen, Norway (PMU); and the Department of Public Health and Primary Health Care, University of Bergen, Bergen, Norway (SEV and GST).

2 Supported by the Norwegian Foundation for Health and Rehabilitation through the Norwegian Health Association, the Johan Throne Holst Foundation for Nutrition Research, the Alzheimer's Research Trust (United Kingdom), the Charles Wolfson Charitable Trust (United Kingdom), the Advanced Research Programme of Norway, the Research Council of Norway, the Foundation to Promote Research into Functional Vitamin B-12 deficiency, and the Norwegian Cancer Society.

3 Reprints not available. Address correspondence to A Vogiatzoglou, Department of Physiology, Anatomy & Genetics, University of Oxford, Le Gros Clark Building, South Parks Road, Oxford OX1 3QX, United Kingdom. E-mail:anna.vogiatzoglou@dpag.ox.ac.uk.

ABSTRACT

Background: Limited information is available on the association between vitamin B-12 status and intake from different dietary sources.

Objective: We investigated the relation of dietary intake of different food items with plasma vitamin B-12 concentrations in the general population.

Design: A cross-sectional, population-based study of 5937 subjects in 2 age groups (47–49 and 71–74 y) from the Hordaland Homocysteine Study in Norway was conducted by using a food-frequency questionnaire and measurements of plasma vitamin B-12 concentrations.

Results: A significant difference in plasma vitamin B-12 concentrations was observed with increasing total vitamin B-12 intake. A plateau was reached at an intake of {approx}10 µg/d. Plasma vitamin B-12 was associated with intakes of increasing amounts of vitamin B-12 from dairy products or fish (P for trend <0.001 for both) but not with intakes of vitamin B-12 from meat or eggs. For the same content of vitamin B-12, intake from dairy products led to the greatest increase in plasma vitamin B-12. Total intake of vitamin B-12, particularly from milk and fish, decreased the risk of vitamin B-12 concentrations <200 pmol/L and impaired vitamin B-12 function (vitamin B-12 <200 pmol/L and methylmalonic acid >0.27 µmol/L) in the total group and in 71–74-y-old subjects.

Conclusions: Dietary intake of dairy products and fish are significant contributors to plasma vitamin B-12 and may improve plasma vitamin B-12 status. Vitamin B-12 appears to be more bioavailable from dairy products; guidelines for improving vitamin B-12 status should take this into consideration.

Received for publication June 26, 2008. Accepted for publication January 6, 2009.