Metformin and Vitamin B12

I've started on metformin a couple of months back (in addition to my insulin), and I asked to have my B12 checked at my next blood draw to be sure, which was not a problem.

I am being tested on Monday along with HbA1c etc, although I have only been on Metformin for 3 months, I mentioned to the nurse that I had read B12 can be affected, so would like it checked. She said OK - guessing it wasn't going to be checked automatically and it must be a cheap test and/or she just wanted to shut me up and get me off the phone! I have been taking a 'hair, nail & skin' supplement for the same amount of time, as diabetes/stress hasn't been kind to the barnet, and that has 240% NRV, so hoping that's enough to balance any ill effects.

Probably too early to tell if Metformin has made any difference though really, but I have never had it checked to my knowledge, so will make sure they keep monitoring so I can keep tabs.

@Andrew2018 if your levels are low at 180, do you know what level is 'normal? Without knowing if that is really really low, or just a bit, can't even guess if 10yrs of Metformin has been 'bad' for your levels.

Andrew2018 said:

I am type 1, been diabetic for over 30 years, and am on metformin due to developing insulin resistance. Once, long ago I was tested for B12 level as it apparently gets affected by metformin in some patients.
I have been having steadily worsening issues with health for over two years, and with a distinct inability to see a GP etc, like most folk. They have just got round to checking B12, the level being 180, and advised taking an oral B12 supplement. I mentioned being tested long ago, and the nurse practitioner didn't know what I was talking about, she had never heard of a link. Questions :- Have you had experience of B12 deficiency due to metformin?. Does your GP regularly check B12?. Since Metformin inhibits intake, anyone know if oral B12 is even going to help?
My diet contains plenty of B12 sources, Metformin has been at 2000mg daily for well over ten years, oh, and interestingly, and possibly related blood pressure medication seems to be distinctly ineffective, increased mononitrate and Doxosozin have had no impact, and wondering if the Metformin is inhibiting their uptake too?. Anyone been in the same boat?

Click to expand...

I take 500 metformin now, and I have been prescribed B12 (I think for my nerves). Whether metformin and B12 are really related I have my doubts. I do know that Vitamin B12 makes me ill all day, so I take the lower OTC One-a-day vitamins.

The leaflet that comes with Metformin now clearly states that Metformin can deplete B12 levels in some people and that B12 levels should be routinely tested. At diagnosis of Type 2 8 years ago I was prescribed 2000mg of Metformin and my B12 levels plummeted. I started using B12 spray and got the levels back to my medium high starting point. Since I stopped taking Metformin my levels have stayed at the same point without supplementation.

Andrew2018 said:

Apparently the B12 vitamin has a huge acceptable range, 180 was apparently regarded as low, then they moved the goal post to something like 140, and the upper end of the range is 900 !.

Click to expand...

Good to know - I will check my Vitamin bottle.

I've recently had my blood tests and was tested for B12 and Folate- mine were low so I'm off to get some supplements. The medical practitioner said it's common with metformin so I think it's worth testing and keeping an eye on....having said that with the supplement's I've been prescribed recently I am going to rattle as I walk- hoping that after a few weeks my energy will be a bit restored- I blame it on a very stressful time at the moment as previous despite very strict keto was not feeling this tired.

Hi @Andrew2018

Bit of a Hobby horse of mine

I found out way after DX the implications of Metformin lowering my B12.

Had NOT been tested
I HAD to request it.
Wasn't an issue, but I think personally it should be part of a yearly check .

From what I have learned.
B12 range is from 180 to 990

Mine came in it 330.

I looked for supplements.
Seems much of those out there can not get through the stomach due to the acid.

Recommendations are to use sublingual
And of a certain type .

Discussion I have come across have likened sublingual efficacy almost on par with injections

I also read that once it gets too low, and it's not treated, it can be irreversible and only option is life long injections, (every 3 months, I think )

That for me was enough to get mine tested.

I haven't had another HBA1c, since 2019 but will be asking for the B12 test once more.


On Metformin.?...the thing they DON'T tell you..Dr Barry explains


If it's of interest
Under my signature is a B movie of Sally pacholok .
I've now put link below here

It outlines what made her suspect people had a deficiency and how it can present.
Not a Hollywood block buster, think more midsomer murders.

But it was still quite an eye opener

Erin said:

I take 500 metformin now, and I have been prescribed B12 (I think for my nerves). Whether metformin and B12 are really related I have my doubts. I do know that Vitamin B12 makes me ill all day, so I take the lower OTC One-a-day vitamins.

Click to expand...

Correction -- that's 500 x2 per day.

Additional info on B12 low tolerance; prescribed 1000mg daily; in case it is affecting my nerves ( I am partly vegetarian )
I am cutting to 500mg. Has anyone taken it, seen an improvement in tingling, esp. legs, hands, feet?

This is an extract from a leaflet produced by Gloucester Hospitals https://www.gloshospitals.nhs.uk/ou...-investigations/vitamin-b12-and-serum-folate/ :-

• Our services
• Services we offer
• Pathology
• Tests and investigations

Dark Horse said:

This is an extract from a leaflet produced by Gloucester Hospitals https://www.gloshospitals.nhs.uk/ou...-investigations/vitamin-b12-and-serum-folate/ :-

B12 Investigation and Treatment Algorithm

Interpretation is difficult. The following observations are offered.

• In clear cut deficiency, levels of B12 are nearly always <150 pg/ml and usually <100 pg/ml.
• Pernicious anaemia is the cause of the majority of severe deficiencies in adults. Around 50% of patients with pernicious anaemia have intrinsic factor antibodies while this antibody is rarely seen in normal controls. Parietal cell antibodies are present in 90% of patients but are also seen in 1 - 2% of normal controls.
• Patients with B12 in the borderline range (150 - 180 pg/ml) may have either early B12 deficiency or be healthy "low normal".
• Neurological disease or glossitis may occur without anaemia or macrocytosis and may be irreversible.
• Interpretation of early megaloblastic change in the marrow is difficult and cannot be reliably distinguished from myelodysplasia.

The following is advised:

Testing should be restricted to those with a suspected vitamin B12 deficiency (macrocytosis, anaemia, neurological deficit, glossitis or clinical condition known to cause B12 deficiency) and should not be used as a screening test.​

When the B12 level is less than 150 pg/ml a presumptive diagnosis of B12 deficiency is made. Where the cause is not known, the laboratory will automatically check for intrinsic factor antibodies. If these are negative, a clinical decision has to be made as to whether further investigation is necessary for patient management. If the B12 is between 150 and 180 pg/ml, a therapeutic trial should be given. If there is a clinical response then a diagnosis of B12 deficiency is made and the appropriateness of further investigation as to cause should be determined.

If there is no response, it is likely that the patient is not B12 deficient and other causes of the clinical problem must be sought.

If further investigation is required, please contact a Consultant Haematologist.​

• Our services
• Services we offer
• Pathology
• Tests and investigations

Click to expand...

YYYEEESSS!!!!! Very informative, thank you.

Hello. I have been on Metformin now for about 23 years with changes in dose at various times. I had a problem with B12 three or four years ago. Long term Metformin use can affect your body's ability to absorb B12 so it makes getting it from your diet more difficult. I wasn't as low as you but had symptoms, so the doctor treated it with tablets. They do work and I was able to come off after 6 months. But B12 levels go back down without them so now I take one every other day which seems to solve the problem for me.
Good luck with getting it sorted out and take care of yourself.
Claire

Andrew2018 said:

I am type 1, been diabetic for over 30 years, and am on metformin due to developing insulin resistance. Once, long ago I was tested for B12 level as it apparently gets affected by metformin in some patients.
I have been having steadily worsening issues with health for over two years, and with a distinct inability to see a GP etc, like most folk. They have just got round to checking B12, the level being 180, and advised taking an oral B12 supplement. I mentioned being tested long ago, and the nurse practitioner didn't know what I was talking about, she had never heard of a link. Questions :- Have you had experience of B12 deficiency due to metformin?. Does your GP regularly check B12?. Since Metformin inhibits intake, anyone know if oral B12 is even going to help?
My diet contains plenty of B12 sources, Metformin has been at 2000mg daily for well over ten years, oh, and interestingly, and possibly related blood pressure medication seems to be distinctly ineffective, increased mononitrate and Doxosozin have had no impact, and wondering if the Metformin is inhibiting their uptake too?. Anyone been in the same boat?

Click to expand...

I’ve been taking Metformin, 2000 mg daily, & about 5 years ago, after complaining about extreme fatigue, a blood test revealed my level at 156. They put me in a series of daily shots & then 1000 mg of B12 daily until present. They check routinely & levels stay around 300-350.