Metformin and B12

Interesting – be careful of B12 deficiency if you’re on this very common diabetes drug.


Every year 20 million prescriptions are written for Metformin, a glucose-lowering drug given to 90% of the 3 million Britons diagnosed with Type 2 diabetes. Yet patients are not being warned that Metformin lowers vitamin B12  and this can trigger peripheral neuropathy – nerve damage, which affects half of diabetics.  It can weaken cardiac tissue raising the risk of heart attack and can cause ulcers which refuse to heal, resulting in an average of 20 amputations a day. 

Surrey University analysed 25 studies involving 7,000 patients and found that taking Metformin for just 4 months is leading to “deficiencies in a significant proportion of patients.”   Dr David Cavan, a leading diabetic expert, says anyone with any sign of neuropathy should have their B12 tested regularly.  He said “We need clinicians to be alert on the issue.”   Acid-reducing medicines often prescribed alongside Metformin to counter the gastric symptoms from the drug, can also reduce vitamin B12.

That is really important information. I would say anyone on it for more than 6 months should get their B12 checked either via the GP or I can do it – I test active B12/HoloTC levels which is different to the serum B12 your GP will do. Have a read here about that:

B12 Deficiency – Under-Diagnosed!

When treating B12 deficiency, it is also important to get the right supplement form. I would go for methyl versions rather than the normal cyanocobalamin as it is much better absorbed and helps with the methylation cycle specifically, which is important. I tend to like sublingual, liposomal, liquid or powder forms and this one is a good version. Sure, it’s more than the one your GP would give you, but I think far better value as it works!

You can also improve your B12 by eating more foods rich in it, of course. Dr Axe has a good summary of B12 generally here and of the food types to go for a bit further down the article.

Vitamin B12 Benefits That You’re Probably Missing

Oh, and by the way, Type 2 diabetes is relatively easy to treat in many cases and you can bring your sugars down so that you need less or even none of the meds. I’ve seen it many times. Start by looking at the Low GL Belly Fat Plan.

Hope that helps.


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