Iron and Levothyroxine Timing: How to Take Them Right

When you're taking levothyroxine, a synthetic thyroid hormone used to treat hypothyroidism. Also known as Synthroid, it needs to be taken on an empty stomach for your body to absorb it properly. If you're also taking iron, a mineral supplement often prescribed for anemia or low iron levels. Also known as ferrous sulfate, it helps rebuild red blood cells, you’ve probably noticed your doctor telling you to keep them apart. That’s not just a suggestion—it’s science. Iron binds to levothyroxine in your gut and blocks its absorption, which can make your thyroid medication useless. The result? You stay tired, gain weight, and your TSH levels stay high—even if you’re taking both pills every day.

So how far apart should you take them? The simplest answer: take levothyroxine first, at least 4 hours before iron. Most people do it first thing in the morning, 30 to 60 minutes before breakfast. Then, take iron at lunch or dinner, or even right before bed. Some people split it up—iron at night, levothyroxine in the morning. That works because your gut clears out most of the iron by morning. Don’t take them together, even if you’re in a rush. Don’t take iron with calcium, magnesium, or antacids either—they do the same thing. And yes, even your morning coffee or high-fiber cereal can interfere. Stick to water with levothyroxine. No exceptions.

It’s not just about timing. It’s about consistency. If you take levothyroxine at 7 a.m. one day and 11 a.m. the next, your hormone levels will swing. That’s why people feel off even when their labs look okay. Same with iron. If you take it with food one day and on an empty stomach the next, your body won’t absorb it the same way. Pick a schedule and stick to it. Track it. Use a pill organizer with morning and night slots. If you forget, don’t double up. Just wait until tomorrow. Your thyroid doesn’t need perfection—it needs predictability.

And if you’re on other meds? Check them too. Calcium supplements, proton pump inhibitors like omeprazole, and even soy milk can mess with levothyroxine. Iron isn’t the only culprit. You’re not just managing two pills—you’re managing a system. That’s why posts here cover things like how ethinylestradiol affects thyroid function, how tamoxifen interacts with other drugs, and why bupropion can change your weight. These aren’t random topics. They’re all pieces of the same puzzle: how your body handles meds when they’re mixed together. Below, you’ll find real, tested advice from people who’ve been there—no fluff, no guesses. Just clear steps to make sure your thyroid stays stable, your iron levels rise, and you stop feeling like you’re always running on empty.