How Can Safely You Take Levothyroxine And Fosamax Together?

In our latest question and answer, the pharmacist discusses how to take two drugs with special administration instructions (levothyroxine and Fosamax), together.

How Can Safely You Take Levothyroxine And Fosamax Together?
Jul 16, 2020

Jan asked

How should I take Fosamax and levothyroxine? I am supposed to take both in the morning but by themselves.

At a glance

  • Alendronate and levothyroxine should not be taken together.
  • Take your alendronate first. Wait a half hour and then take your levothyroxine dose.


Hi Jan and thank you for contacting us. This is a great question because both medications are ideally taken first thing in the morning on an empty stomach, with no other drugs, for optimal absorption. These medications are very commonly prescribed and many people take both... so you are in the same situation as a lot of people!

First, these shouldn’t be taken together. Alendronate (or under the brand, Fosamax) is an oral bisphosphonate used to help maintain strong bones. Levothyroxine is a synthetic thyroid hormone used to treat hypothyroidism. If you take both of these at the same time, you won’t absorb the full dose of the alendronate. The dose you absorb of levothyroxine could be lessened too, which can make a significant impact since doses of levothyroxine are so small (remember that it is does in micrograms, not milligrams).

I think the easiest way to manage is to take the alendronate first. Hopefully, you’re on the once weekly dose so you’ll only have to worry about this once a week. I would wake up, take your alendronate dose with a full glass of water, and then remain upright for at least 30 minutes (this helps to prevent GI irritation).

After 30 minutes, the majority of the dose should be absorbed. Then I would take your morning levothyroxine dose. Again, take it with a glass of water. After 30-45 minutes the majority of the dose should be absorbed, and you can eat breakfast and begin to go about your normal day.

The most important thing is to take these drugs consistently for best effects. This is especially true for levothyroxine. Taking it inconsistently, for example with food one day and on an empty stomach the next, will lead to changes in how much is absorbed. This will likely cause fluctuations to your TSH levels which will make it hard to determine the correct dose you should be on.

Thanks for reaching out to us and I hope this helps.

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