Is it Safe to Take Levothyroxine and Vitamin B12?
Yes, it is generally safe to take vitamin B12 with levothyroxine, and in many cases, it is necessary for individuals with hypothyroidism. While there is no direct chemical interaction between the two, an important consideration is how and when you take them, particularly if the vitamin B12 is part of a multivitamin containing minerals. The main concern is not the vitamin B12 itself, but the potential for certain minerals, like iron and calcium, to interfere with the absorption of levothyroxine in the gut.
For this reason, timing and consistency are crucial. The American Thyroid Association recommends taking levothyroxine on an empty stomach, either 60 minutes before breakfast or at bedtime, at least three hours after your evening meal. Multivitamins or supplements containing interfering minerals should be taken at least four hours away from your levothyroxine dose to prevent any absorption issues.
The Connection Between Hypothyroidism and B12 Deficiency
A significant portion of people with hypothyroidism are also deficient in vitamin B12, and this isn't a coincidence. The link is often rooted in autoimmune disease.
- Autoimmune Connection: The most common cause of hypothyroidism is Hashimoto's thyroiditis, an autoimmune disease. Individuals with one autoimmune condition are more likely to develop another. This increases the risk for pernicious anemia, another autoimmune disorder where the body attacks a protein called intrinsic factor, which is essential for B12 absorption.
- Overlapping Symptoms: The symptoms of B12 deficiency—such as fatigue, weakness, poor memory, and mood changes—are very similar to those of hypothyroidism. This can lead to persistent symptoms even after thyroid hormone levels are stabilized with levothyroxine. For these reasons, many experts recommend screening for B12 deficiency when hypothyroidism is diagnosed and re-testing periodically.
How to Properly Schedule Your Medications and Supplements
Proper timing is the key to ensuring both your levothyroxine and any necessary supplements, including B12, are absorbed effectively. Follow these guidelines to create a consistent and effective routine.
- Consistent Timing: Take your levothyroxine at the same time every day. This helps maintain stable thyroid hormone levels. The best options are first thing in the morning (30-60 minutes before breakfast) or at bedtime (at least 3 hours after your last meal).
- Separate Supplements: If your B12 is part of a multivitamin with minerals like calcium or iron, schedule it for a different time of day, at least four hours away from your levothyroxine dose.
- Pure B12 Supplements: If you are taking a B12-only supplement, the risk of interaction is minimal. However, taking it at a separate time from your levothyroxine is still a good practice to ensure optimal absorption for both.
Types of Vitamin B12 Supplements
There are several forms of B12 supplementation, and the best choice depends on the severity of your deficiency and absorption capabilities.
- Oral Tablets: Oral supplements are common and effective for many people. It is important to find a high-quality product, especially one containing methylcobalamin, which is highly bioavailable.
- Sublingual (Under the Tongue) Drops or Sprays: These forms bypass the digestive system and are absorbed directly into the bloodstream, making them a good option for those with absorption issues.
- B12 Injections: For individuals with severe B12 deficiency, pernicious anemia, or significant malabsorption, a doctor may prescribe injections. This method ensures the vitamin enters the bloodstream directly, completely bypassing any potential interference from the gut.
Comparison Table: Best Practices for Levothyroxine and B12
| Practice | Correct Method | Incorrect Method | Rationale |
|---|---|---|---|
| Levothyroxine Timing | Take on an empty stomach, 30-60 mins before breakfast or 3+ hours after dinner. | Take with breakfast, coffee, or calcium/iron supplements. | Ensures maximal and consistent absorption of the thyroid hormone. |
| Multivitamin/B12 Timing | Take multivitamins containing calcium or iron at least 4 hours away from levothyroxine. | Take a multivitamin at the same time as levothyroxine. | Minerals like calcium and iron can bind to levothyroxine and decrease its effectiveness. |
| B12-only Supplement Timing | Can be taken separately from levothyroxine to avoid interference. | Taking at the same time can interfere with absorption of levothyroxine. | While less likely to interfere, a 4-hour separation is a safe, conservative approach for oral supplements. |
| Addressing Overlapping Symptoms | Work with your doctor to test B12 levels if hypothyroid symptoms persist. | Assume lingering symptoms are just from hypothyroidism. | Symptoms like fatigue and brain fog can be caused by both deficiencies, so proper diagnosis is necessary for complete symptom relief. |
Conclusion
Combining vitamin B12 supplements and levothyroxine is safe and often necessary, but it must be done with careful attention to timing to avoid compromising the efficacy of your thyroid medication. The primary rule is to never take levothyroxine at the same time as a multivitamin containing minerals like iron or calcium. By taking levothyroxine alone on an empty stomach and spacing out your supplements by at least four hours, you can ensure proper absorption of both. Given the high prevalence of B12 deficiency in hypothyroid patients, especially those with autoimmune issues, it is a conversation worth having with your healthcare provider to help address overlapping symptoms and optimize your overall health management.
Authoritative Outbound Link
For further information on how certain supplements and foods interact with thyroid medication, you can refer to guidance from trusted health organizations. Read more about dietary supplements and thyroid disease from Verywell Health.
