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Can I Take Vitamin B12 And Levothyroxine Together

Can I Take Vitamin B12 And Levothyroxine Together - Hormone Replacement Therapy

If you’re managing thyroid issues with levothyroxine and wondering about adding vitamin B12 to your regimen, you’re not alone.

Patients often seek to optimize their thyroid health by supplementing with vitamins, but it’s essential to understand how these supplements interact and whether taking them together is safe.

Role of Levothyroxine As Thyroid Medication

Levothyroxine is a synthetic form of thyroid hormone prescribed to treat hypothyroidism, a condition where the thyroid gland doesn’t produce enough hormones.

It works by replacing or supplementing the body’s natural thyroid hormones, helping to regulate metabolism and energy levels.

Can I Take Vitamin B12 And Levothyroxine Together


Interaction between Vitamin B12 and Levothyroxine

While there’s generally no direct interaction between vitamin B12 and levothyroxine, vitamin B12 supplements can affect the absorption of levothyroxine in some individuals. To minimize the interaction risk, it is recommended that they be taken at least two hours apart.

Timing of Supplement Intake

Taking vitamin B12 supplements at least two hours apart from levothyroxine allows sufficient time for the absorption of each medication without interference. This helps ensure that both medications are absorbed effectively and provide the intended benefits.

Recommended Dosages


Vitamin B12

For most adults, the recommended daily intake (RDI) of vitamin B12 is 2.4 micrograms (mcg). However, individuals with a deficiency may require higher doses for treatment.

Treatment for vitamin B12 deficiency typically involves oral supplements, with doses ranging from 1000 to 2000 mcg per day. 

Different forms of supplementation are available, including oral capsules (400-1000 mcg per day), sublingual B12 (1000-5000 mcg per day), and injections (5000 mcg weekly).



For primary hypothyroidism, initial doses typically range from 1.6 mcg/kg orally once a day for otherwise healthy individuals to 12.5-25 mcg orally once a day for those over 50 years or with cardiovascular disease. 

In cases of severe, longstanding hypothyroidism, initial doses may also start at 12.5-25 mcg orally once a day. The maintenance dose of levothyroxine is approximately 1.6 mcg/kg/day, considered a full replacement dose. 

The maximum daily dose is usually 200-300 mcg, although doses greater than 300 mcg daily are rarely needed and may indicate poor compliance or malabsorption issues.

Side effects

Common side effects of levothyroxine include headache, fatigue, weight changes, and changes in appetite. Vitamin B12 supplements are generally well-tolerated but can cause nausea, diarrhea, and skin rash in some people. 

Potential Benefits of Taking Vitamin B12 with Levothyroxine

Taking vitamin B12 alongside levothyroxine, a medication used to treat hypothyroidism, may offer several potential benefits:

Enhanced Energy Levels

Both vitamin B12 and levothyroxine play roles in energy metabolism. Vitamin B12 produces red blood cells, which carry oxygen to tissues, while levothyroxine helps regulate metabolism. 

Together, they may help combat fatigue and increase energy levels, especially in individuals with hypothyroidism who often experience fatigue as a symptom.

Improved Cognitive Function

Adequate levels of vitamin B12 are essential for proper brain function and cognitive health. Some studies suggest vitamin B12 deficiency may contribute to cognitive decline and memory impairment. 

By ensuring sufficient vitamin B12 levels, especially in individuals with hypothyroidism, cognitive function may be better preserved.

Better Mood Regulation

Both vitamin B12 and levothyroxine influence neurotransmitter synthesis and function, which play crucial roles in mood regulation. Deficiencies in either nutrient can lead to symptoms of depression, anxiety, or irritability. 

Supplementing with vitamin B12 alongside levothyroxine may help support mental well-being and mood stability.

Enhanced Nutrient Absorption

Hypothyroidism can affect digestive function and nutrient absorption, leading to deficiencies in essential vitamins and minerals, including vitamin B12. 

Taking vitamin B12 supplements alongside levothyroxine may help address deficiencies and improve overall nutrient absorption, promoting better overall health.

Potential Cardiovascular Benefits

Both vitamin B12 and levothyroxine are involved in cardiovascular health. Vitamin B12 plays a role in homocysteine metabolism, and elevated homocysteine levels are associated with an increased risk of cardiovascular disease. 

Levothyroxine, by optimizing thyroid function, may also indirectly benefit cardiovascular health. Together, these nutrients may contribute to a healthier cardiovascular profile.

Things To Avoid During Thyroid Medication

Things To Avoid During Thyroid Medication - Hormone Replacement Therapy

When undergoing thyroid medication, there are certain things to avoid to ensure the treatment’s effectiveness and prevent potential complications. Here are some key things to keep in mind:

Inconsistent Medication Timing

Taking thyroid medication simultaneously each day and on an empty stomach, preferably in the morning, is crucial to ensure consistent absorption.

Avoid taking it with food, supplements, or medications that can interfere with absorption, such as calcium or iron supplements, antacids, or certain medications like proton pump inhibitors.

Dietary Interactions

Certain foods and beverages can affect thyroid medication absorption or thyroid function. These include high-fiber foods, soy products, cruciferous vegetables (such as broccoli, cabbage, and Brussels sprouts), and excessive amounts of caffeine. 

While it’s unnecessary to avoid these foods altogether, it’s advisable to consume them in moderation and at least several hours apart from taking thyroid medication.

Calcium and Iron Supplements

Calcium and iron supplements can impair the absorption of thyroid medication when taken simultaneously. To minimize interference, it’s best to take these supplements at least four hours apart from thyroid medication.

Herbal Supplements

Some herbal supplements, particularly those containing kelp or seaweed, may contain high levels of iodine, which can affect thyroid function. It’s essential to consult with a healthcare provider before taking any herbal supplements, especially if you’re undergoing thyroid medication.

Alcohol and Tobacco

Excessive alcohol consumption and smoking can negatively impact thyroid function and interfere with the effectiveness of thyroid medication. It’s advisable to limit alcohol intake and avoid smoking to support thyroid health and medication efficacy.

Stress and Poor Sleep

Chronic stress and inadequate sleep can disrupt thyroid function and exacerbate symptoms of thyroid disorders. Practicing stress-reduction techniques, adequate sleep, and a healthy lifestyle can help support thyroid health and optimize medication effectiveness.

Inadequate Monitoring

Regular blood test monitoring of thyroid function is essential to ensure that medication dosage is appropriate and thyroid levels are within the optimal range. 

Avoid skipping scheduled appointments with your healthcare provider and follow their recommendations for closely monitoring thyroid function.


While taking vitamin B12 supplements alongside levothyroxine is generally safe, it’s essential to be mindful of potential interactions and follow your healthcare provider’s recommendations. 

By understanding how these medications interact and taking them as directed, you can support your thyroid health effectively. If you have any concerns or experience adverse effects, consult us at Hormone Replacement Therapy LA for personalized advice and guidance.

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