Vitamin B12, also known as “cobalamin,” is a water-soluble essential nutrient required in our diet. When a nutrient is essential, it means the body cannot produce it internally so it must come from food we eat or supplemental form.
If you have type 2 diabetes, you could be at higher risk of a vitamin B12 deficiency. Vitamin B12 supports a healthy nervous system, brain and red blood cells and is needed only in very small amounts (2.4 mcg/day).
Vitamin B12 is found only in meat, poultry, fish, eggs, and dairy, which is why vegetarians and especially vegans are at higher risk for deficiency and should take a dietary supplement that includes B12. While there is no set upper limit for B12, it is useless to supplement if you do not have a deficiency.
Blood levels <200 pg/mL are generally considered deficient while >400 pg/mL are sufficient. Between this range, you may want to consider supplementation. Dosing will vary depending on level of deficiency, but is often 1-2 mg daily. In some cases mega-dose injections every month are required, depending on how the person responds to supplementation or if there is a severe deficiency.
What Does Vitamin B12 Do?
Vitamin B12 plays a number of very important roles in our bodies:
- It is necessary for the metabolism of amino acids and fatty acids
- It is required for DNA synthesis
- It helps synthesize neurotransmitters (ie serotonin and dopamine)
- It is essential for cardiovascular function
Vitamin B12 Deficiency and Type 2 Diabetes
It’s estimated that 22% of people with type 2 diabetes have Vitamin B12 deficiency, which is much higher than the general population.
Getting enough Vitamin B12 in your diet through the food you eat is only one piece of the picture. After it has been ingested, the B12 then needs to be absorbed from the gut into the body, then travel to the cells to do its work. Vitamin B12 requires something called “intrinsic factor” (a protein secreted by special cells in the stomach) in order to be absorbed from the lumen of the gut into the body. Some people don’t make as much intrinsic factor, and generally speaking, as we get older, we make less and less, which is a reason why the elderly are at higher risk for B12 deficiency, too.
Additionally, metformin (a first line drug commonly used in diabetes treatment), is one of many medications that interferes with absorption of Vitamin B12. It has been estimated that 10-30% of people who take metformin may not be able to absorb Vitamin B12. Another study showed that 75% of metformin users were deficient. Whether the range is 10% or 75%, it's still something to be concerned about – if you're taking metformin, you are at higher risk for B12 deficiency.
Interestingly, it also seems to be the case that B12 deficiency may cause hyperglycemia (high blood sugar levels) so there may be a bit of a cyclical relationship between the two.
One of the complications of type 2 diabetes is neuropathy (numbness/pain that often first appears in the hands and feet). Neuropathy is experienced by about 30% of people with diabetes. Deficiency of B12 is associated with neuropathy as well and it can be difficult to tell which may be causing the symptoms or if both may be contributing.
People who have had bariatric surgery are at high risk for deficiency also, since their absorptive area has been reduced and the portion of the stomach that secreted intrinsic factor may be gone or destroyed.
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Signs of Vitamin B12 Deficiency
Early signs of vitamin B12 deficiency may include:
- Tiredness
- Weakness
- Weight loss (unintentional)
- Loss of appetite
- Constipation
- *B12 deficiency can also be asymptomatic or without symptoms, especially in early stages
If left untreated, long term B12 deficiency can lead to:
- Permanent brain and nerve damage
- Memory Loss
- Dementia
- Depression
- Immobility
Diagnosing Vitamin B12 Deficiency
If you think you might have B12 deficiency, discuss your symptoms with your doctor and request he/she test your levels. There is a very simple blood test and treatment is as easy as supplemental doses.
There are several options for supplementing. Oral pills or sublingual (means ‘under the tongue’) options are available over the counter. Often, if intrinsic factor is lacking, periodic mega-dose B12 injections are administered. These shots are given into the muscle and are very effective. Obviously this would have to be performed in your doctor’s office.
If you are a vegetarian or vegan, over the age of 50, have any medical issues with absorption (including any type of gut surgery or condition), or take metformin, you are at much higher risk and should be tested regularly.
Top Sources of Dietary Vitamin B12
- Liver
- Clams
- Caviar
- Fish – mackerel, herring, salmon, tuna, cod, trout
- Crab
- Organ meats – kidney, heart, giblets, brains
- Eggs
- All meats and poultry
Include the above foods regularly in your diet and your intake of B12 should be sufficient. If you're a vegetarian or especially a vegan, it is highly recommended you take a supplement.
There are also other food items that have been fortified with B12 such as: nutritional yeast, breakfast cereals, breads and sometimes tofu – but in many cases, these are foods we would not necessarily recommend for a low carb T2 diabetic diet. Stick to the natural food sources because they are a much better option.
Just know though, if you are deficient in vitamin B12, it is very unlikely you will be able to correct the problem through food alone, but will likely need to include a supplemental form, at least for a time.
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Celery and Type 2 Diabetes
I have type 2 diabetes and have very low B12 levels. I also take metformin. I have tried various B12 supplements including injections and always end up with diarrhea as a result. Any suggestions? Thanks
Hi Laura,
Mild diarrhea can often be a side effect of B12 supplementation. It could help to space out the dosing throughout the day. Also, a probiotic in conjunction with your supplement may help.
Thanks so much info on the B-12. 😳
Glad you found it helpful!
Wonderful. Information
I was put on metformin and suffered with bowl problems and extremely low B12 . I also have a under active thyroid and blood pressure , all a bad combination. I had to have B 12 injections which helped for a short time. Then they found my vitamin D levels were very low. The fatigue I suffer from has altered my life and I just want to feel less tired all the time and have some life again
Claire, all these imbalances with in your body are likely huge contributors to the fatigue you are experiencing recently. Continue to work with your health care team address the thyroid concerns, but make sure your consuming plenty of vegetables, nuts, protein, and some fruit to give your body the right nutrition to balance itself. Having high blood sugar frequently can also cause fatigue, but luckily those foods I just mentioned should help keep your blood sugar pretty steady as well.
Very useful article.
Is iron tablets the same as b12?
No Josie, they are two entirely different nutrients.
Thank you so much this was very helpful to me.🙌
I just recieved my labs that a neurologist ordered and my 2 hour gloucose test was 178, I have low T3 free, low T4 free but normal TSH and B12 is 249. What could all of this mean. I have been sick for a LONG time .
Your 2 hour glucose test is higher than normal Cathy, in the prediabetic range. T3, T4 and TSH are all thyroid hormones and B12 is a vitamin, which all may be out of balance. You really need to speak to your neurologist about the rationale behind having these tests done and what they mean. Good luck – I hope you find a solution and feel better soon.
very helpful article for layman thanks
I have pernicious anaemia and was diagnosed with type 2 diabetes a year ago. I have B12 injection regularly and am on insulin as well as metformin. I find it difficult to cope sometimes especially with the fatigue.
I get a yearly blood work up for my diabetes. Do I have to specifically ask for a B12 test to be included?
Yes Tony. Even though they should include it they mostly don’t unless you request it.
My husband just saw a specialist that tested him for the deficiency among other things that the regular doctor did not. So ask for the additional testing to be done with your blood work.
Well put together. Very informative.
thank you for the information.. it may helps me..
Just came upon your site and I believe everyone should be tested yearly for B12 Deficiency. I just found out that my B12 levels were 196…Yiks! The doctor immediately started me on b12 injections and I had to have one per week for 4 weeks. I had 5 total and now take 1000 mg’s of sublingual drops daily. I will go back for a followup in a couple months to see where my levels are at that time. I noticed something was wrong when my hair was falling out a lot and I was loosing my strength when opening a simple jar. So please have yours checked to be safe.
Definitely, it is recommended to have regular checks since it is a deficiency that is common in diabetes. Glad you uncovered yours and can correct the problem Cheryl. Best of luck!
Thank you for this notice, because my sister in law suffers From memory Loss. So I’ve been doing research on vit B12 and I find this could be her problem. When my sister suffered from memory loss we found out that she was Severely low in vitamin B12. It took over a year of Vitamin b12 shots, for her to get better.
Yikes–that sounds scary. So glad they caught it. B12 deficiency can be difficult to detect since it affects the brain. Keep up with the research–the more educated you are, the better your shot at preventing complications!