How much Vit B12 should you take for Hypothyroidism.

Inside: Underactive thyroid and its connection with B12 deficiency. What are low B12 and thyroid symptoms? Also how much and what form of B12 to take to support thyroid.

Vitamin B12 deficiency is very commonly associated with Thyroid disorders. Especially in autoimmune thyroid disease like Hashimoto’s; the prevalence of vitamin B12 deficiency is very high. 

The worst part is that the symptoms of B12 deficiency can sometimes be easily missed, especially if you have low thyroid. So it is very important to have a high index of suspicion and check B12 levels. 

Underactive Thyroid and B12 Deficiency 

Now the bigger question is why is B12 deficiency so highly prevalent in thyroid patients.

There are various reasons and it can be dietary related. Also, certain people are at higher risk for B12 deficiency as compared to others.

Like vegetarians, vegans and elderly are all at higher risk for B12 deficiency.

Another big reason for people with thyroid disorders to have low B12 levels is — antibodies against the parietal cells (which helps with B12 absorption).

This condition is also called pernicious anemia. Where the body develops antibodies against the parietal cells and destroys them. Parietal cells secrete what is called intrinsic factor which is required for the absorption of B12 in our gut.

According to this study, the prevalence of B12 deficiency in autoimmune thyroid patients was 28%, so it is not a rare phenomenon but very common.

In another study, the prevalence of low B12 was 55% in patients with autoimmune thyroid disease.

The second study raised another important question that — a single test to check for Vitamin B12 levels in the blood might miss a lot of patients which might be deficient in B12 and not picked up by that test!

So to make sure the B12 deficiency does not get undetected – we suggest looking at different markers like MMA, homocysteine levels also in conjunction, in addition to B12 deficiency blood tests.

Recommended Thyroid SupplementPure Encapsulation Liquid B12

B12 and Thyroid Symptoms 

Upon discussion of B12 and Thyroid relation, most people will have this question — what are the symptoms of B12 deficiency in thyroid patients?

The huge problem is that the symptoms of B12 deficiency and low thyroid overlap, so it make the situation a little tricky to catch in the first place.

The most common symptoms of B12 deficiency are

  • Tiredness and fatigue
  • Constipation
  • Mood changes 
  • Tingling or numbness in hands and feet

Interestingly the majority of these symptoms are also attributed to low thyroid.

So that’s the reason it becomes difficult to differentiate until we check for B12 deficiency.

The most concerning symptoms is the peripheral nerve damage that occurs because of B12 deficiency and that can easily be avoided with supplementation from B12, so again very important in thyroid patients to for deficiency of B12. 

Tests for B12 deficiency

Unfortunately, the blood tests that are ordered to check for vitamin B12 deficiency don’t give the true picture of functioning B12 in your system and can sometimes miss suboptimal B12 levels.

Vitamin B12 levels in the blood is often an inaccurate reflection of your B12 status and also there are some concerns about the range that is being used in the labs which are very broad often from 200-900 ng/ml.

The broad range can miss the patients whose levels might be on the lower end of the spectrum and still have symptoms.

For complete evaluation getting a combination of tests is the best way to check for B12 status.

The following test can be done by any standard lab and can help to evaluate your B12 status —

  1. Vitamin B12 serum levels 
  2. MMA levels 
  3. Homocysteine levels. 

The way these tests are interpreted are very different and have to be carefully understood. I feel Vitamin B12 serum levels should be more than 300ng/ml and ideally above 400ng/ml.

MMA levels have to be understood carefully, as the high MMA levels indicate low B12 status, any MMA level above 300 nmol/l is concerning for me and reflect suboptimal B12. Homocysteine levels reflect the functioning status of B12 and we want these levels to be less than 10.

So based on these tests people can evaluate their B12 status and take supplementation accordingly.

What kind of B12 to Take and How Much

This is the Thyroid Supplement I suggest to my patients.

Now you got your blood work checked and it came back that you are B12 deficient, so how much and what form and which route to take B12.

B12 comes in oral tablets, Intramuscular injections and also sublingual tablets.

The concern is that in thyroid patients there is a problem with B12 absorption because of the antibodies against intrinsic factor as explained above.

So the oral route might not be the best way of supplementation for people with thyroid dysfunction.

For my patients with autoimmune thyroid conditions like Hashimoto’s, I recommend them sublingual or Intramuscular injection.

Both of them are good ways to get your B12 levels up, in fact, a study was done which showed equal efficacy of sublingual as compared to injectable B12. I generally recommend sublingual 1000mcg of B12 daily.

Here’s the B12 Supplement I suggest to my patients for Thyroid.

The injectable will have different dosage generally around 1000 mcg once a week initially for 1 month and then 1000mcg once a month. 

The prevalence of Vitamin B12 deficiency is higher in underactive thyroid patient especially Hashimoto’s.

Often low B12 and thyroid symptoms are very similar, so clinically it makes it harder for physicians to diagnose B12 deficiency.

The best way is to have a high index of suspicion for B12 deficiency in thyroid patients and check their levels. A comprehensive panel to check for B12 and how to interpret these results is also important. Also how to supplement B12 and how much of B12 to take with hypothyroidism is critical for your health. 

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References: 

Ness-Abramof R1, Nabriski DA, Prevalence and evaluation of B12 deficiency in patients with autoimmune thyroid disease.Am J Med Sci. 2006 Sep;332(3):119-22.

Wang YP, Lin HP. Hemoglobin, iron, and vitamin B12 deficiencies and high blood homocysteine levels in patients with anti-thyroid autoantibodies.J Formos Med Assoc. 2014 Mar;113(3):155-60. doi: 10.1016/j.jfma.2012.04.003. Epub 2012 Jun 29.

Jaya Kumari S, Bantwal G Evaluation of serum vitamin B12 levels and its correlation with anti-thyroperoxidase antibody in patients with autoimmune thyroid disorders.Indian J Clin Biochem. 2015 Apr;30(2):217-20. doi: 10.1007/s12291-014-0418-4. Epub 2014 Feb 6.

Velarde-Mayol C1, de la Hoz-García B. Pernicious anemia and autoimmune thyroid diseases in elderly people. Rev Esp Geriatr Gerontol. 2015 May-Jun;50(3):126-8. doi: 10.1016/j.regg.2014.10.004. Epub 2015 Jan 8.

Bensky MJ, Ayalon-Dangur I. Comparison of sublingual vs. intramuscular administration of vitamin B12 for the treatment of patients with vitamin B12 deficiency.. Drug Deliv Transl Res. 2019 Jun;9(3):625-630. doi: 10.1007/s13346-018-00613-y.

How much Vit B12 should you take for Hypothyroidism.

About The Author

Dr. Anshul Gupta, MD

I am Dr.Gupta, a Functional Medicine and Integrative Medicine physician. I like to write about Functional medicine approach to managing different diseases and want to empower people to reclaim their health through this modern approach. Come join me on this healing journey.

How much Vit B12 should you take for Hypothyroidism.

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