Levothyroxine and Food Interactions: What to Eat and Avoid

When you take levothyroxine, a synthetic thyroid hormone used to treat hypothyroidism. Also known as synthroid, it works best when your body can absorb it fully—something many people unknowingly sabotage with what they eat or drink. Levothyroxine isn’t like other pills. Its absorption is sensitive, and even small changes in your routine can make it less effective. If you’re still feeling tired, gaining weight, or struggling with brain fog despite taking your dose, food interactions might be the hidden culprit.

Calcium, a mineral found in dairy, supplements, and fortified foods is one of the biggest disruptors. Drinking milk, eating yogurt, or taking a calcium supplement within four hours of your levothyroxine can block up to 30% of the drug from entering your bloodstream. The same goes for iron, often found in multivitamins or anemia treatments. If you take iron pills in the morning with your thyroid med, you’re essentially canceling out half the dose. Even soy, common in tofu, soy milk, and protein shakes can interfere—studies show it lowers absorption by reducing how much levothyroxine your gut lets through.

Here’s what actually works: take levothyroxine on an empty stomach, first thing in the morning, with a full glass of water. Wait at least 30 to 60 minutes before eating or drinking anything else—not even coffee. If that’s not doable, take it at bedtime, four hours after your last meal. That’s the second-best option, and many people find it easier to stick with. Avoid grapefruit juice, high-fiber meals, and antacids too—they all mess with absorption. Don’t rely on feeling better to know it’s working. Blood tests are the only real way to tell if your dose is right.

People often think they can just take their thyroid pill whenever they remember. But consistency matters more than you think. Swapping from morning to night, or eating oatmeal right after your dose, might seem harmless—but it’s enough to throw your hormone levels off track. That’s why your doctor keeps checking your TSH levels. It’s not just routine—it’s your body telling you whether the medication is getting through.

Below, you’ll find real-life advice from people who’ve fixed their levothyroxine issues by changing how and when they take it. You’ll also see what other medications and supplements clash with thyroid treatment, and how to spot when your dose needs adjusting. No fluff. Just what works.