Deb asked
I take Levothyroxine 137mg. Is it safe to take a b12 vitamin, collagen, and a multivitamin?
Answer
There is a significant interaction between Synthroid (levothyroxine) and multivitamins. Many different substances (foods and minerals such as calcium, aluminum and magnesium) are known to decrease Synthroid (levothyroxine) absorption if taken at the same time. The most common mechanism behind the decreased absorption is due to "chelation".
Calcium, and a variety of other mineral and drugs, can bind (i.e. chelate) to Synthroid (levothyroxine), which can significantly decrease the absorption of the medication. Decreased absorption of Synthroid (levothyroxine) will, in most cases, lead to increased thyroid stimulating hormone (TSH) levels and the need to increase the dose of Synthroid (levothyroxine).
Multivitamins contain multiple ingredients that are known the bind to Synthroid (levothyroxine), decreasing absorption such as:
- Calcium
- Iron
- Magnesium
- Manganese
- Potassium
- Zinc
To ensure consistent absorption of Synthroid (levothyroxine), it is recommended to take the medication on an empty stomach with a full glass of water, at least 30 to 60 minutes before food (most commonly breakfast). It is very important to take Synthroid (levothyroxine) apart from substances known to decrease absorption.
If morning dosing isn't possible, it is important to know that consistency of administration is key to avoid fluctuating thyroid levels in the body (resulting from variable Synthroid (levothyroxine) absorption with interacting substances). Synthroid (levothyroxine) can be taken in the evening, as long as it has been 4 hours after the last meal of the day, when the stomach is mostly empty.
If it is not possible to separate Synthroid (levothyroxine) from food in your situation, try to take the medication at the same time daily, with the same foods or same interval away from food. This will ensure consistent absorption and thyroid levels in the body.
Below is a list of the most common foods, medications and supplements that are known to decrease Synthroid levels when taken together:
- Multi-vitamins
- Antacids (especially calcium and aluminum containing ones)
- H2 Blockers
- PPIs (Proton Pump Inhibitors)
- High calcium foods (e.g. dairy)
- Bisphosphonates (e.g. Fosamax)
- Coffee
- Grapefruit juice
- Iron
- Magnesium
- Bile acid sequestrants
- Simethicone
- Soy
- Fiber
