Vitamin B 12 Supplementation for Hypothyroidism

Vitamin B12 is a water-soluble vitamin found in a variety of foods and is also available as a dietary supplement and prescription medication.1 It is has several forms and has the mineral cobalt in it. Vitamin B12 is used for creating red blood cells, DNA synthesis and neurological function.1

Natural vitamin B12 is bound to protein in foods, when hydrochloric acid and gastric protease are activated in the stomach it causes the release of vitamin B12 from protein.1 For fortified foods and dietary supplements, vitamin B12 is free and not bound to protein and does not need to be unbound.1 Vitamin B12 is currently used for thyroid disease, particularly hypothyrodism.1

What is Hypothyroidism?

Hypothyroidism is a condition in which the thyroid gland does not produce enough thyroid hormone.2 When hormone production is limited due to the thyroid gland not functioning properly, it can negatively influence numerous chemical reactions in the body.2 The thyroid gland helps regulate metabolism of numerous body functions such as reproduction, DNA synthesis, temperature, and heart rate.

Some factors that can cause hypothyroidism include autoimmune disease, thyroid surgery, radiation therapy, and medications.2 Symptoms include fatigue, weight gain, slowed heart rate, elevated blood cholesterol level, dry skin, constipation and sensitivity to cold and an enlarged thyroid gland (goiter).2 Hypothyroidism can be treated by many thyroid medications, but there are some studies out there demonstrating vitamin B12 supplementation and its possible role in hypothyroid management.3

How does vitamin B12 help with hypothyroidism?

In a hospital-based study in north Indian population, the role of vitamin B12 and thyroid stimulating hormone was tested in dementia patients.3 Vitamin B12 deficiency is a modifiable factor in patients with dementia that if left untreated can increase the risk of Alzheimer’s dementia (AD) or vascular dementia (VaD).3

Serum vitamin B12 levels were studied in 32 patients with an average age of 65 years.3 In patients with AD and VaD levels of vitamin B12 were lower.3 Thyroid-stimulating hormone was also lower compared with control subjects.3 This study concluded that Vitamin B12 supplementation should be considered for therapeutic intervention in dementia patients and can assist with low TSH patients.3

A study was done to see the prevalence and clinical features of B12 deficiency in hypothyroid patients and evaluate response to symptoms in B12 replacement.4 A total of 116 subjects with hypothyroidism (95 females and 21 males) were evaluated.4 46 patients had low vitamin B12 levels and among males and females prevalence was the same.4

Mean Hb in b12 deficient patients was 11.9 vs. 12.4 in the sufficient group.4 Symptoms such as impaired memory, numbness, depression, weakness, and slow reflexes were seen more often in vitamin B12 deficient patients but was not statistically significant in this study.4 24 study patients with vitamin B12 deficiency received intramuscular B12 injections monthly and a little more than 50% demonstrated improved symptoms.4

How do you take vitamin B12?

The Recommended Dietary Allowance (RDA’s) for vitamin B12 depends on the age of the person.1 For ages 14+ Male is 2.4mcg and Female is 2.4mcg in the pregnant population 2.6mcg and for lactation 2.8mcg.1 Vitamin B12 is found naturally in many food products such as milk, meat, poultry, eggs and fish.1 It is also in fortified breakfast cereals so vegetarian eaters can get vitamin B12 as well.1 In addition to natural foods vitamin B12 is in oral dietary supplements and its important to note about 10mcg of a 500mcg oral supplement is absorbed.1

Dietary supplements can come in the form of lozenges or sublingual tablets.1 Vitamin B12 can also be found in the form of prescription medications.1 Cyanocobalamin and hydroxocobalamin can be given as an injection into the muscle.1 These prescription medications are used to treat vitamin B12 deficiency in patients with pernicious anemia among other conditions.1 Prescription B12 also comes in a nasal gel spray formulation and can be an option for patients not wanting the parenteral form.1

Safety of Vitamin B12

Vitamin B12 is generally safe and well-tolerated as it is found in a variety of healthy foods such as whole grains and dairy products like yogurt and milk, meats and eggs.1 In the NORBIT (0.4mg for 40 months) and HOPE 2 (1.0 mg for 5 years) trials vitamin B12 in combination with folic acid and vitamin B6 led to no serious adverse effects.1 Currently, the IOM has no established upper limit for vitamin B12 because of its low toxicity potential.

Vitamin B12 does have the potential to interact with certain medications such as those used for gastroesophageal reflux disease (GERD)1 Proton pump inhibitors (PPIs) can interfere with Vitamin B12 absorption from food due to the drugs ability to slow the release of gastric acid. In H2 receptor antagonists absorption of vitamin B12 can be interfered with because of the release of hydrochloric acid into the stomach. In metformin used for diabetes absorption of vitamin B12 can occur by intestinal mobility changes. It is important to consult with your provider to see if vitamin B12 is appropriate for you.


Natural herbs for hypothyroidism such as Vitamin B12 is one of the many supplements for hypothyroidism that can be used to assist patients to achieve better thyroid levels and control.1,3 Vitamin B12 come in a variety of forms including tablets, natural foods, injectables, and even a nasal spray.1

Although well tolerated by most patients this vitamin has the potential to interact with medications including metformin for diabetes and PPIs and H2RA commonly used for GERD.1 Many studies have proven vitamin B12’s positive role in hypothyroidism patients.1 If you are planning on using vitamin B12 for your hypothyroidism, please consult your healthcare provider to make sure it is safe and appropriate for you.


  1. “Office of Dietary Supplements – Vitamin B12.” NIH Office of Dietary Supplements, U.S. Department of Health and Human Services, 30 Mar. 2020,
  2. “Hypothyroidism (Underactive Thyroid).” Mayo Clinic, 7 Jan. 2020,
  3. Agarwal, Rachna et al. “Role of vitamin B(12), folate, and thyroid-stimulating hormone in dementia: A hospital-based study in north Indian population.” Annals of Indian Academy of Neurology 13,4 (2010): 257-62. doi:10.4103/0972-2327.74193
  4. Jabbar, Abdul et al. “Vitamin B12 deficiency common in primary hypothyroidism.”  The Journal of the Pakistan Medical Associationvol. 58,5 (2008): 258-61.