# Link Between Metformin and Neuropathy, B12 Deficiency



## Northerner (Oct 10, 2015)

The link between metformin and vitamin B12 lowering is well-known and mentioned in American Diabetes Association guidelines as a disadvantage of the drug. However, there are no recommendations for monitoring and prevention of vitamin B12 deficiency for patients taking metformin. Vitamin B12 deficiency is associated with adverse effects such as fatigue, mental status changes, and neuropathy. Given the prevalence of neuropathy in diabetic patients, metformin-induced vitamin B12 deficiency is clinically relevant.

The relationship between vitamin B12 deficiency and metformin was studied in a recent randomized placebo-controlled trial. The trial lasted 52 months and included 390 type 2 diabetes patients. They were treated with 850 mg metformin at doses up to three times a day or placebo. Patients with baseline vitamin B12 deficiency or patients taking vitamin B12 supplements were excluded from the trial.

http://www.diabetesincontrol.com/link-between-metformin-and-neuropathy-b12-deficiency/


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## KookyCat (Oct 11, 2015)

It's about time they did something about this.  In the US B12 levels is a standard test for people using Metformin and my uncle tells me for all diabetics (Metformin is used in the US for things other than diabetes).  Course they also have to agree what a realistic base level is for B12 because it differs from one country to the next, in some a base of 500 is appropriate and for others it's 2000.  The really disturbing thing is it's known that Metformin interferes actively with B12 and they just ignore the fact here that long term Metformin use can cause a persistent low level deficiency.  B12 deficiency causes neuropathy, visual impairment, dry mouth, extreme fatigue, and ultimately it can be fatal.  More disturbingly B12 has recently been implicated as a possible causal factor in shingle, Motor Neurone Disease and MS (which is apparently often the first diagnosis when someone has a severe B12 deficiency, it was my initial diagnosis).  

They've never understood how diabetes causes neuropathy, initial theories suggested it was glucose molecules invading the nerve fibres but that's never held water.  The latest research is suggesting that high blood sugar increases thirst and the increase in consumption of water washes the B12 out of the body.  Since it's a water soluble vitamin you lose a good proportion of it through your kidneys.  You need B12 to conduct electrical signals.  It's worth keeping an eye on your B12 I would say.  The one good thing about my doctors surgery is they elect to test B12 which is good, but they don't all do it.  My Dad was tested just before he died and his level was 40 a level that is incredibly dangerous, and was listed as one of the complications of diabetes (along with nerve damage to his heart) that contributed to his death.


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## Worcester_Matt (Oct 11, 2015)

My mum has long-term B12 deficiency (first diagnosed when she was pregnant with me). She took metformin for about a year before she was able to come off it as her glucose levels were low enough with diet and exercise alone. I'm wondering if I should have my B12 levels tested (not that I'm on metformin, but I have a lot of neuropathy and some of the other symptoms of B12 deficiency).


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## KookyCat (Oct 11, 2015)

I'd check, me and my Dad both had B12 deficiencies and shared a genetic abnormality of the protein in the stomach that helps to break it down.  Plus it can't hurt to check, and might help with the neuropathy


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## Karsten (Jan 5, 2019)

i read about this and stopped metformin as i was severely fatigued.. started taking metylB12 sublingual..
improved no end and in single digits first time since diagnosed.
difficult getting diagnosed tho if you take supplements.

my pee is bright yellow sometimes due to soluble B vitamins but prefer that to being fatigued all day , unable to dream, remember, concentrate etc..
think I have perm neuropathy damage though.


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## mikeyB (Jan 5, 2019)

This is a very complex situation. The early symptoms of B12 deficiency are glossitis ( smooth, slightly inflamed tongue), a pale yellow tinge to the skin, tiredness, and tingling in the hands and feet. If you only have that tingling, it’s not likely to be caused by low B12. 

That said, I have no doubt that testing for B12 deficiency should be as routine as the HbA1c in folk taking Metformin, it’s criminal not to.

As Kookycat says, severe B12 deficiency can be fatal, and can be initially confused with other neurological disorders, but B12 deficiency is a routine test done by neurlogists these days because of that. There is no confirmed link between low B12 and MS or MND. Those conditions can’t be alleviated by B12 therapy; the neurological symptoms of B12 deficiency can be corrected with therapy, though some symptoms may remain.


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## Karsten (Jan 6, 2019)

> inflamed tongue..
kept biting my tongue told GPs and they ignored it.
Also had shingles last year after being prescribed metropramide..
if I mention that to GPs they all say nothing to do with it.

testing
> it’s criminal not to.
Never had a B12 test until I showed my GPs the articles about B12 and metformin.. and then complained..
My serum B12vwas 260  in feb and had severe fatigue in June..
GP insisted 160 was the limit..  but if you read the articles under 300 can be too little.

>B12 deficiency is a routine test done by neurologists
Try getting a GP to order one..
a serum B12 isn't good enough they need to order a Metyl Malonic Acid test as that is why a B12 deficiency is dangerous.
You should not have any MMA in your blood.  If B12 deficient you'll have it in your blood and it attacks your heart nerves arteries (all the long term side effects of diabetes)
But GPs won't order it, too expensive.

The fact that stopping metformin and taking metyl B12 has stopped most of the fatigue, tingling, reduced my sugars and improved my memory, enabled me to dream again tells me a lot.
You can't overdose on B12 so I'm going to make sure I have enough.

The really irritating thing is if you try to get a GP to report anything negative about metformin or any drug they are not interested.


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## mikeyB (Jan 6, 2019)

Not all GPs. Some keep up to date. My GP on Mull informed me that the tiredness and muscle weakness I was experiencing ( before all this neuro thing started) was probably due to hypomagnesaemia through taking Omeprazole. Sure enough, I did have dangerously low Magnesium, and supplements put me right. I was impressed, I didn’t know about that.

It doesn’t happen regularly in folk taking Omeprazole, but it can happen.


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## trophywench (Jan 6, 2019)

@mikeyB  - my pharmacist told me that Omeprazole and Clopidogrel don't play nicely together at all, and changed it to Lanzaprazole.  Wonder if it was the magnesium effect he was referring to?


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## mikeyB (Jan 6, 2019)

lanzaprozole and Omeprazole are both proton pump inhibitors and have similar side effects, including hypomagnesemia. The Ranitidine I now take is an H2 antagonist. 

Lanzaprozole equally should be used with caution with Clopidogrel, according to the literature. Your pharmacist and GP ought to know that.


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## Lilian (Jan 6, 2019)

mikeyB said:


> This is a very complex situation. The early symptoms of B12 deficiency are glossitis ( smooth, slightly inflamed tongue), a pale yellow tinge to the skin, tiredness, and tingling in the hands and feet. If you only have that tingling, it’s not likely to be caused by low B12.



When I was first diagnosed with Pernicious Anaemia my only symptom was tingling in the hands.  My feet just felt like they were burning at night.    However at the same time it was discovered that I was also deficient in T3 of the thyroid with low T4 (and low TSH).   Hence me taking a private blood test because NHS would not do them.    I started B12 injections and taking liothyronine at the same time.    Tingling in hands went, burning feet went, and other symptoms.   So I cannot pin point to whether it was a thyroid matter, a B12 matter or both.    I might have eventually got the other symptoms of B12 deficiency, but at that time tingling and numbness of the hands was the only one, and not all day, only in the mornings.


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