Advice from Dr Gill Jenkins, a GP and flight medical officer with a special interest in diabetes and weight management, who herself has type 2 diabetes.

Do not stop taking your metformin. Your medicine is essential for blood sugar control and the benefits it provides far outweigh any impact on nutrient absorption.

Proton pump inhibitors (PPIs) are anti-acid medications which are often prescribed in people of this age group for concurrent gastric reflux, and they have also been shown to impair nutrient absorption. But if you are taking a prescribed PPI, do not stop treatment without consulting your doctor, and if you are taking a PPI which is available over-the-counter, speak to a pharmacist or your GP.

PPI’s commonly prescribed in the UK include omeprazole — which is sold under brand names including Prilosec, Losec, Mepradec and Zegerid — esomeprazole, which is sold as Nexium, and lansoprazole, known by the brand-name Zoton FasTabs.

Both metformin and PPI’s are associated with lower levels of vitamin B12 and deficiency may potentially cause peripheral neuropathy, a form of nerve damage which can also occur if there is chronically high blood sugar and is a complication of poorly controlled diabetes.

Many people with diabetes do not develop peripheral, or diabetic, neuropathy but when it occurs, the impact can be devastating. It can lead to loss of sensation in the feet, which increases the risk of minor injuries going unnoticed and developing into infections and ulcers. It may also damage muscle in vital organs, resulting in irregular heart rhythm, digestive problems, incontinence and impotence and can lead to muscle wasting, which increase the risk of falls.

Although there are some glimmers of hope, most experts believe that once neuropathy occurs, the damage cannot be reversed — so preventive is paramount.

At your next review, ask your clinician, doctor or specialist nurse if your vitamin B12 levels are being monitored. If they are not, request B12 screening alongside your normal blood sugar and HbA1c checks.

In the meantime, it makes sense to eat a healthy diet which rich in vitamin B12 take a daily multi-vitamin containing useful amounts of vitamin B12 and vitamin D. Do not take high doses of single vitamins without consulting your healthcare provider.

Good dietary sources of vitamin B12 include meat, fish, eggs, dairy products, yeast extracts (such as Marmite and some fortified breakfast cereals. In a perfect world, a healthy balanced diet should provide all the nutrients we need, but the evidence that metformin can disrupt absorption of vitamin B12 and folate (also known as folic acid or vitamin B12) is beyond doubt.

As is true of a number of nutrients, our ability to absorb vitamin B12 declines with age and is also affected by alcohol consumption. As animal proteins are the best sources of vitamin B12, vegetarians and vegans are also at increased risk of deficiency.

Signs of vitamin B12 deficiency include:

  • Tiredness
  • Weakness
  • Constipation
  • Loss of appetite
  • Weight loss
  • Tingling or numbness in the hands and/or feet
  • Megaloblastic anaemia
  • Balance problems
  • Depression
  • Confusion
  • Poor memory, and
  • Soreness of the mouth or tongue.

People with diabetes are also more likely to be lacking vitamin D, which plays an important role in blood sugar control.

We make most our vitamin D from sunlight on our skin, so during autumn and winter deficiency is common as there is not enough sunshine for our bodies to synthesise it and we must rely on stores built up over summer.

For this reason, the Department of Health now advises: “People should consider taking a daily supplement containing 10 micrograms of vitamin D in autumn and winter.”

There are often no outward symptoms of vitamin D deficiency, but warning signs include:

  • Tiredness
  • Vague aches and pains
  • A general sense of not being well
  • Muscle weakness
  • Difficulty climbing stairs, getting up from the floor or a low chair
  • Walking with a waddling gait
  • Bone pain in the lower back, hips, pelvis, thighs and feet


Eat regularly and stick to a healthy diet with lean proteins, plenty of fruit and vegetables and starchy carbohydrates with a low glycaemic index.

If you are overweight, aim to lose between 5% and 10% of your body weight — but any weight loss will help.

If you smoke, quit, or consider switching to e-cigarettes as a harm-reduction measure. They have not been around long enough to be sure they are safe, but experts agree they are SAFER than smoking.

Get active. Physical activity not only reduces the risk of developing diabetes, it helps manage it by helping the body use insulin more efficiently; increasing the amount of glucose your muscles use, which may lower your blood sugars; strengthening bones; reducing stress and depression and improving sleep.

Coordinate meals and medicines to avoid dips and spikes in blood sugar levels, but always carry a snack or glucose in case your blood sugars drop too low.

Stay hydrated but avoid sugar-sweetened drinks.


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  • https://www.practicalpainmanagement.com/resources/news-and-research/anti-muscarinic-drugs-may-reverse-peripheral-neuropathy
  • Berchtold P, Dahlqvist A, Gustafson A, Asp NG. Effects of a biguanide (metformin) on vitamin B12 and folic acid absorption and intestinal enzyme activities. Scand J Gastroenterol 1971;6:751-4.
  • Chapman LE, Darling AL, Brown JE. Association between metformin and vitamin B12 deficiency in patients with Type 2 Diabetes: A systematic review and meta-analysis. Diabetes Metab. 2016 Nov;42(5):316-327.http://epubs.surrey.ac.uk/811166/22/DMMetformin21-3-16FINALR2AuthorPostRefereeVersion_withfigures.pdf
  • Laufer EM, et al. Effects of moderate alcohol consumption on folate and vitamin B(12) status in postmenopausal women. Eur J Clin Nutr. Nov;58(11):1518-24. https://www.ncbi.nlm.nih.gov/pubmed/15138463
  • https://ods.od.nih.gov/factsheets/VitaminB12-Consumer/
  • Takiishi T, Gysemans C, Bouillon R & Mathieu C. Vitamin D and diabetes. Endocrinology and Metabolism Clinics of North America 2010 39 419–446. https://www.ncbi.nlm.nih.gov/pubmed/20511061
  • https://patient.info/health/osteoporosis-leaflet/vitamin-d-deficiency
  • https://www.nice.org.uk/guidance/ng28/ifp/chapter/diet-and-lifestyle
  • https://www.diabetes.org.uk/guide-to-diabetes/managing-your-diabetes/exercise
  • https://www.mayoclinic.org/diseases-conditions/diabetes/in-depth/diabetes-management/art-20047963
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