Sunday, September 11, 2011

B12 Pills Instead of Shots and Metformin

People who are unable to absorb vitamin B12 in their diet can usually do fine with B12 pills instead of shots. I am amazed to see so many still getting the inconvenient costly intramuscular injections of vitamin B12 when they would do fine with B12 pills instead of shots. 
And vitamin B12 pills are available over the counter without a prescription.

A dose of 250 micrograms of vitamin B12 a day should be fine in most people. Those diagnosed with pernicious anemia or gastrointestinal problems may need 1000 micrograms daily. These findings on the use of B12 pills instead of shots are not new.

What is relatively new is the finding that people taking metformin for Type 2 Diabetes are about 5 times more likely to get vitamin B12 deficiency. 11 percent more of the metformin users in a recent randomized controlled trial had low vitamin B12 levels compared to the non-users of metformin. It is likely that metformin reduces absorption of vitamin B12 from the intestine.

I recommend a yearly blood test measurement of vitamin B12 levels in my patients on metformin. Methylmalonic acid (MMA) increases in the blood when there is vitamin B12 deficiency so an elevated level of MMA confirms vitamin B12 deficiency. But other conditions such as reduced kidney function can increase the MMA. And a low or borderline vitamin B12 level even without an elevated MMA may still be appropriate to supplement with vitamin B12.

Absorption of vitamin B12 is very complicated. Animal products, mostly meat and fish, are dietary sources of vitamin B12. Vitamin fortified breakfast cereals and multivitamin supplements also contain vitamin B12. 

6 micrograms is the Recommended Daily Intake (RDI) of vitamin B12.
So most of those vitamin B12 pills contain a lot more than the RDI. The high doses allow for most people needing a supplement to get adequate levels with B12 pills instead of shots.

Many people as they get older have problems absorbing vitamin B12 even if they don't take metformin. And a multivitamin supplement may not be adequate.

Vitamin B12 is important for brain and nerve function and blood cell formation.
It seems reasonable to supplement vitamin B12 when the level is low even before symptoms occur. There is no evidence of problems by doing so. And symptoms from low B12 can be confused with other conditions, like diabetic neuropathy.

A high level of vitamin B12 does not appear to be harmful. But it’s appropriate to monitor vitamin B12 levels in people taking supplements.

By the way, there is no benefit shown from sublingual vitamin B12 over vitamin B12 pills.

Vitamin B12 pills instead of shots can be used by most people and metformin users should have B12 levels checked. Are you on a vitamin B12 supplement?

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