Vitamin B12 Deficiency and Diabetes

Braden G. Barnett, MD

2021 Sep 29

10 min read

Vitamin B-12 is an essential vitamin for diabetes patients as it promotes healthy blood cells and nervous system. According to a study, almost 22% of people with diabetes were low in B-12, suggesting that metformin is the reason. 

Diabetic patients should choose a diet that contains B12, else they will face a severe deficiency of this vitamin. Mellitus Diabetic patients can easily develop a B12 deficiency as they are at a higher risk. It is because diabetics mostly take metformin, which is a well-known treatment of Type-2 diabetes.

You don’t have to take Vitamins supplements if you are facing a minor B12 deficiency. You can obtain it through meat, poultry, fish, and dairy products. Let’s discuss vitamin B12 deficiency, its reasons, and why its deficiency is serious for diabetes patients. 

What is Vitamin B12?

Vitamin B12, being a water-soluble vitamin, is also known as cobalamin. This vitamin is essential for the proper functioning of the body. Due to deficiency of B12 vitamin, the level of blood glucose decreases. People usually take this vitamin along with folate and other vitamin B complexes.

Major Causes of Vitamin B12 Deficiency

Some people are vegetarian or vegan and don’t eat animal products at all. Almost all such people who don’t eat meat and dairy products are deficient in vitamin B12. Vegans and vegetarians are more prone to its deficiency just because vitamin B12 is not present in plants. 

You might be thinking about how you can take vitamin B12 naturally when you are a vegetarian. Well, you can fulfill vitamin B12 intake through energy bars and breakfasts having fortified B12. Not only are consuming vitamins and minerals healthy, but your body should also absorb them efficiently. 

Besides an imbalance diet, undersupply of IF (Intrinsic Factor) protein also causes vitamin B12 deficiency. Under normal routine, stomach cells create this protein. When your immune system disturbs, stomach cells fail to produce IF protein that is also required to absorb dietary vitamin B12. 

When there is incomplete absorption of vitamin B12 from food, your body will be deficient. To make your body function smoothly, you should also take medications for the effective absorption of B12. 

How does absorption of Vitamin B12 take place?

In the human body, the small intestine is the part where absorption of Vitamin B12 takes place. When IF binds with Vitamin B12, a vitamin B12-IF complex forms, this complex plays a vital role in the absorption of vitamin B12 in your body. 

Medications To Boost Vitamin B12 Absorption

You can boost the absorption of vitamin B12 in your body by taking the following medications:

1- An antibiotic- known as chloramphenicol

2- Metformin containing Glumetza and Glucophage for treatment of diabetes type 2.

3- Medications of peptic ulcer and acid reflux disorder including Omeprazole (Prilosec), Famotidine (Pepcid AC), Ranitidine (Zantaz), and Lansoprazole (Prevacid)

Why is the deficiency of Vitamin B12 so serious for diabetic patients?

Vitamin B12 deficiency is very serious because it leads to certain complications, including diabetes and anemia. In diabetes, blood glucose level goes low beyond a certain limit. While in anemia, the number of healthy red blood cells to carry out oxygen depletes. 

Another serious thing that may happen to vitamin B12 deficient people is loss of smell and taste sensations. Some people suffer from serious symptoms such as shortness of breath, dizziness, fatigue, and a fast heartbeat. 

You may also suffer from diabetic neuropathy due to a lack of vitamin B12. In peripheral neuropathy, you will experience weakness, pain, and numbness in your hands, legs, and feet. Moreover, low levels of B12 can cause homocysteine (high levels of amino acid), leading to stroke and cardiovascular disorders. 

In short, the long-term deficiency of vitamin B12 causes serious symptoms like depression, delusion, difficulty in walking, loss of mobility, seizures, and dementia. Make sure to take a regular intake of this vitamin for diabetes and treatment of other diseases.

Long-term Vitamin B12 Deficiency Leads to Diabetic Neuropathy

When you do not treat your vitamin B12 deficiency, you may face severe diabetic complications. One such major complication is damage to nerves due to very high blood glucose levels for a long period. 

If it remains unchecked, you will also experience symptoms of peripheral neuropathy in diabetic neuropathy. These symptoms are pain and numbness in the arms, legs, hands, and feet. Besides this, diabetic neuropathy will also affect the gastrointestinal tract of your body. 

Moreover, neuropathy is not only because of prolonged diabetic conditions. But prolonged vitamin B12 deficiency can also cause it. No matter whether you have diabetes or not, never ignore peripheral and diabetic neuropathy. Regulate your body’s diabetes level by regulating the amount of vitamin B12. 

How does Vitamin B12 deficiency occur in Diabetics?

Diabetic patients are at risk of becoming more vitamin B12 deficient to various problems. In both diabetes type 1 and type 2, diabetic patients experience its deficiency. Let’s read how type 1 and 2 diabetes affect the level of Vitamin B12 in your body. 

Diabetes Type 1

People with diabetes type 1 are usually at higher risk of getting autoimmune disorders like thyroid problems and coeliac disease. Such patients are also more vulnerable to pernicious Armenia. In anemic conditions, the body automatically produces antibodies against the vitamin B12 carrier, i.e., Intrinsic Factor (IF). 

Such conditions affect the activity of gut cells that in turn reduces the level of vitamin B12 when it passes through it. When vitamin B12 does not reach the small intestine, it will not be absorbed properly, causing vitamin B12 deficiency. 

Diabetes Type 2

Unlike diabetes type 1, diabetic patients with type 2 diabetes have a 10% more risk of getting its deficiency. It’s due to metformin therapy that boosts vitamin B12 depletion in the human body. 

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Moreover, the risk of vitamin B12 deficiency also increases with increased metformin dose and duration of its use. In most cases, this depletion takes place 3 to 4 months after starting this therapy. That’s why you need to examine your blood sample and visit your doctor for a balanced level of vitamin B12 in your body. 

Effect of Metformin on Vitamin B12 Deficiency

By using metformin for a long period, the absorption of vitamin B12 will be reduced in your body. According to research studies, nearly 30 percent of diabetic patients suffer less vitamin B12 absorption in their intestines. 

Vitamin B12 deficiency due to metformin occurs because it interferes with the complex of B12-IF. To activate receptors of your small intestine, you also have to take calcium regularly for complete absorption of vitamin B12. It depicts that vitamin B12 absorption is a calcium-dependent process. 

A study shows that vitamin B12 increases due to the inductive effect of metformin by increasing calcium intake. That’s why it is said that calcium reverses the absorption of vitamin B12 and diabetes. Take supplements of calcium regularly along with metformin to stimulate the absorption of vitamin B12. 

Increase Vitamin B12 Intake in your Diet To Stabilize Glucose Level in Your Body

You can control blood glucose level in your body by increasing intake of vitamin B12. When it comes to increasing the level of vitamins for diabetes, people usually take supplements. At the same time, it’s better to use natural dietary fibers like foods rich in vitamin B12. Many such vitamin B12 rich foods can be obtained from animal and non-animal sources. 

Here are some main sources from which you can improve your diabetic condition:

Animal source vitamin B12 rich foods are eggs, fish, poultry, meat (including lamb, pork, and beef), and dairy products (including cheese and milk)

Non-animal sources of vitamin B12 are vegetables and plants, including Korean purple laver and mushrooms

Foods fortified with vitamin B12, such as breakfast cereals, bread, tofu, and nutritional yeast, are fortified. 

Though all vegetables and plants don’t have vitamin B12, there are still some plant-based sources. In a journal article on plant-based vitamin B12 sources, researchers have claimed that purple larval and mushrooms are very healthy and rich sources of B12. 

Treatment of Vitamin B12 Deficiency 

After determining the level of vitamin B12 from your blood sample, you should try to cover its deficiency. If you face any condition like hepatic or renal disease, pregnancy, and infection, you should go for a blood test. Consult your doctor to analyze the blood sample report to assess the level of essential vitamins and minerals. 

Through this, not only your vitamin B12 level can be examined, but also your folate level does. The best way to treat low-level of vitamin B12 is by excessive intake of fortified bread, cereals, eggs, and milk. Also, add a good amount of green leafy vegetables to your diet. Avoid drinking goat milk because it’s low in folate and vitamin B12. 

Which one is better: Vitamin B12 Supplements Vs. Intramuscular Injection?

The first thing you should keep in mind while treating vitamin B12 deficiency is to act upon a doctor’s prescription. Never take a supplement or injection at your own decision. Because there is a possibility that taking vitamin B12 pills will not be the right choice for you. 

It’s not only the vitamin B12 that we intake orally. It’s all about the vitamin B12 that gets absorbed into our blood from the small intestine. If you are suffering from an absorption problem, taking more vitamins will do nothing better for you. Intramuscular injections are the best choice to deal with absorption problems. 

Warning: Consult your Doctor first before treating vitamin B12 deficiency either way. 


1- Does vitamin B12 is crucial for lowering blood sugar?

Well, vitamin B12 does not play a role in the management of blood glucose levels. Instead of lowering blood glucose levels, the level of vitamin B12 gets lowered itself in diabetic patients. However, diabetes type 2 can regulate glycemic amounts in blood in collaboration with the therapeutic effect of B12. The only way to recover from your condition of hyperhomocysteinemia is by taking a regular dose of vitamin B12, vitamin B6, and folic acid. 

2- Is Vitamin B complex healthy for diabetic patients?

Yes, vitamin B complex is very healthy for people with diabetes as it only interferes with medications for diabetes. There are various vitamins of group B which are effective in lowering blood sugar levels. Such vitamins are vitamin B1, vitamin B6, biotin, thiamin, and pyridoxine. Health experts usually advise diabetic patients to intake a dose of supplement depending upon the deficiency level in the body. On average, diabetic patients should take 300 mcg of biotin, 150 mcg of B12, 1.5 mg of B1, 75 mg of B6, 25 mg of B2, and 2.5 mg of folic acid. 

3- How much vitamin B12 can you take in metformin therapy for diabetics?

There is a need to inject diabetic patients with a dose of 1mg. Using metformin therapy for a long time is a cost-effective and practical treatment of blood glucose level maintenance. Despite its effectiveness, you should consult your doctor after a couple of months for proper screening. Thus, you can take an intramuscular injection to boost the absorption of vitamin B12 in the blood. 

4 – How long do vitamin B12 supplements take to work for diabetes treatment?

Generally, vitamin B12 supplements start showing their effect after 48 to 72 hours of the initial dose. If you face a serious problem maintaining glucose, taking a vitamin B12 injection for almost 3 months will help you bring things in balance. 

Final thoughts

Vitamin B12 deficiency in diabetic people is quite common. Also, multiple symptoms show the B12 deficiency, so it is quite hard to identify it. So, consult with your doctor if you are at high risk or have any of the symptoms. However, you can prevent the B-12 deficiency by taking a proper diet and supplements.

Written by

Braden G. Barnett, MD

Dr. Braden G. Barnett is an endocrinologist in Los Angeles, California and is affiliated with multiple hospitals in the area, including Keck Medical Center of USC and USC Norris Comprehensive Cancer Center. He received his medical degree from University of Southern California and has been in practice around 8 years. A skilled professional, Dr. Barnett holds certification from the American Board of Internal Medicine with a special focus on endocrinology, diabetes, and metabolism. He is also a recipient of several awards and honors.

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