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mrsD · 04-22-2009, 08:59 AM

This question comes up very frequently.

One has to understand that the research information about B12 has changed radically in the last 10 years. Not all doctors are aware of these changes.

This link, to a physician website, is one good one to start with:
http://www.aafp.org/afp/20030301/979.html
(it can be copied and taken to your own doctor)

It brings up the question of oral vs injectable. (and was put on the net in Mar. 03),

Oral can work well for most people. I should be taken on an empty stomach, because passive absorption is how the B12 is going to be absorbed in the intestine. Drugs given in microgram doses, cannot be absorbed reliably with food/fiber present. The amounts are so small they are lost in the food (like a sponge).
Digoxin and thyroid hormone also are in this category. So since B12 is a microgram nutrient, it should have the same recommendation.

For people with poor stomach acid levels (due to genetics or drugs used), it is estimated that about 10% or less of the B12 is actually absorbed. So the apparent high dose taken orally is not
something to be afraid of. Labels often show %RDA on them and those huge numbers for B12 often frighten patients unnecessarily. (example==66,000 % of RDA etc)

Here are two other research papers showing oral B12 is as effective as injectable:

Quote:

Am Fam Physician. 2009 Feb 15;79(4):297-300.Links
Evidence for the use of intramuscular injections in outpatient practice.
Shatsky M.

Providence Medical Group, Portland, Oregon, USA. mlsdo2000@comcast.net

There are few studies comparing the outcomes of patients who are treated with oral versus intramuscular antibiotics, corticosteroids, nonsteroidal anti-inflammatory drugs, or vitamin B12. This may lead to confusion about when the intramuscular route is indicated. For example, intramuscular ceftriaxone for Neisseria gonorrhoeae infection and intramuscular penicillin G benzathine for Treponema pallidum infection are the treatments of choice. However, oral antibiotics are the treatment of choice for the outpatient treatment of pneumonia and most other outpatient bacterial infections. Oral corticosteroids are as effective as intramuscular corticosteroids and are well-tolerated by most patients. High daily doses of oral vitamin B12 with ongoing clinical surveillance appear to be as effective as intramuscular treatment. Few data support choosing intramuscular ketorolac over an oral nonsteroidal anti-inflammatory drug unless the patient is unable to tolerate an oral medication. For other indications, the intramuscular route should be considered only when the delivery of a medication must be confirmed, such as when a patient cannot tolerate an oral medication, or when compliance is uncertain.

PMID: 19235496 [PubMed - indexed for MEDLINE]

from http://www.ncbi.nlm.nih.gov/pubmed/1...ubmed_RVDocSum

and

Quote:

Fam Pract. 2006 Jun;23(3):279-85. Epub 2006 Apr 3.Click here to read Links
Oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiency: a systematic review of randomized controlled trials.
Butler CC, Vidal-Alaball J, Cannings-John R, McCaddon A, Hood K, Papaioannou A, Mcdowell I, Goringe A.

Department of General Practice, Cardiff University, Wales, UK.

BACKGROUND: Vitamin B(12) deficiency is common, increasing with age. Most people are treated in primary care with intramuscular vitamin B(12). Several studies have reported equal efficacy of oral administration of vitamin B(12). OBJECTIVES: We set out to identify randomized controlled trial (RCT) evidence for the effectiveness of oral versus intramuscular vitamin B(12) to treat vitamin B(12) deficiency. METHODS: We conducted a systematic review searching databases for relevant RCTs. Outcomes included levels of serum vitamin B(12), total serum homocysteine and methylmalonic acid, haemoglobin and signs and symptoms of vitamin B(12) deficiency. RESULTS: Two RCTs comparing oral with intramuscular administration of vitamin B(12) met our inclusion criteria. The trials recruited a total of 108 participants and followed up 93 of these from 90 days to 4 months. In one of the studies, mean serum vitamin B(12) levels were significantly higher in the oral (643 +/- 328 pg/ml; n = 18) compared with the intramuscular group (306 +/- 118 pg/ml; n = 15) at 2 months (P < 0.001) and 4 months (1005 +/- 595 versus 325 +/- 165 pg/ml; P < 0.0005) and both groups had neurological responses. In the other study, serum vitamin B(12) levels increased significantly in those receiving oral vitamin B(12) and intramuscular vitamin B(12) (P < 0.001). CONCLUSIONS: The evidence derived from these limited studies suggests that 2000 microg doses of oral vitamin B(12) daily and 1000 microg doses initially daily and thereafter weekly and then monthly may be as effective as intramuscular administration in obtaining short-term haematological and neurological responses in vitamin B(12)-deficient patients.

PMID: 16585128 [PubMed - indexed for MEDLINE]

from http://www.ncbi.nlm.nih.gov/sites/en...&term=16585128

I personally don't think sublingual vs oral swallow is much of an issue. I don't believe that sublingual works very well. This form has historically been the favorite OTC version, but B12 is a huge molecule and water soluble and not likely to cross the small area under the tongue in reasonable amounts of time. What really happens is that the sublingual dissolves and the resultant saliva is swallowed. And what can happen is that the tablet kept under the tongue may irritate tissues over time, and cause inflammation in sensitive people or those reactive to flavors or sweeteners. If you want to dissolve your sublingual under the tongue fine, but I don't think you HAVE to.