Levothyroxine is absorbed best on an empty stomach with water. As a general pattern, wait about 30–60 minutes before coffee or food, and about 4 hours from calcium, iron, magnesium, antacids, bile acid binders and soy. Enter your own dose time in the tool and it returns the earliest clock time for each item, plus the reason and how well documented it is. Nothing is stored and the schedule is calculated in your browser.
| Item | Type | Separation from dose | Why |
|---|---|---|---|
| Plain water | Drinks | No separation needed | Water is how levothyroxine is meant to be taken. A full glass helps the tablet dissolve and reach the small intestine. (Well documented) |
| Coffee (including black) | Drinks | Wait 1 hour after the dose | Coffee taken with or shortly after the tablet measurably lowers absorption. Most clinicians advise waiting 30–60 minutes; this tool uses 60 as the safer default. (Well documented) |
| Coffee or tea with milk | Drinks | Wait 4 hours after the dose | Two issues at once: the coffee effect plus calcium from milk, which binds levothyroxine. Treat it like a calcium source. (Reasonably documented) |
| Black or green tea | Drinks | Wait 1 hour after the dose | Less studied than coffee, but the same practical caution applies to anything other than water in the first hour. (Limited evidence — cautious default) |
| Grapefruit juice | Drinks | Wait 1 hour after the dose | Modestly reduces levothyroxine absorption in controlled studies. Usually a small effect, but easy to separate. (Reasonably documented) |
| Breakfast or any food | Food | Wait 30 minutes after the dose | Levothyroxine is absorbed best on an empty stomach. Thirty minutes is the usual minimum; 60 is better if your routine allows. (Well documented) |
| High-fibre meal or fibre supplement | Food | Wait 4 hours after the dose | Dietary fibre and bulking agents bind levothyroxine in the gut and reduce how much reaches the bloodstream. (Reasonably documented) |
| Soy foods (tofu, soy milk, soy protein) | Food | Wait 4 hours after the dose | Soy reduces levothyroxine absorption. The advice is not to eliminate soy but to keep intake consistent and separated, then retest labs. (Reasonably documented) |
| Walnuts | Food | Wait 4 hours after the dose | Reported to interfere with absorption in case literature. Evidence is thin, so this is a cautious default rather than a firm rule. (Limited evidence — cautious default) |
| Milk, yoghurt or cheese | Food | Wait 4 hours after the dose | A calcium source. Calcium binds levothyroxine, so it belongs in the four-hour group with supplements. (Well documented) |
| Calcium supplement or fortified drink | Supplements | Wait 4 hours after the dose | Calcium carbonate forms an insoluble complex with levothyroxine. Four hours of separation is the standard advice. (Well documented) |
| Iron supplement (ferrous sulfate, bisglycinate) | Supplements | Wait 4 hours after the dose | Iron binds levothyroxine directly. Four hours apart is standard — and low ferritin is worth correcting, not avoiding. (Well documented) |
| Multivitamin containing iron or calcium | Supplements | Wait 4 hours after the dose | Most multivitamins carry both of the main binders. Check the label — if either is listed, separate by four hours. (Well documented) |
| Magnesium supplement | Supplements | Wait 4 hours after the dose | Magnesium salts and antacids containing magnesium reduce absorption in the same way calcium does. (Reasonably documented) |
| Selenium supplement | Supplements | No separation needed | No documented absorption interaction. Take it whenever suits you — but stay within safe upper intakes. (Reasonably documented) |
| Vitamin D supplement | Supplements | No separation needed | No meaningful timing interaction on its own. If it is in a combined calcium tablet, follow the calcium rule instead. (Reasonably documented) |
| Biotin (often in hair/skin/nail formulas) | Supplements | No separation needed | Biotin does not change absorption, but it can distort thyroid lab assays and make results look wrong. Blood tests: Stop biotin at least 48 hours before a thyroid blood test, or tell the lab you take it. (Well documented) |
| Proton pump inhibitor (omeprazole, pantoprazole) | Medications | Wait 4 hours after the dose | Reduced stomach acid can lower levothyroxine absorption. Separation helps; some people also need a dose review — ask your prescriber. (Reasonably documented) |
| Antacids (aluminium or magnesium based) | Medications | Wait 4 hours after the dose | Bind levothyroxine directly in the gut. Four hours apart is the usual instruction. (Well documented) |
| Bile acid binders (cholestyramine, colesevelam) | Medications | Wait 4 hours after the dose | Among the strongest binders of levothyroxine. Some prescribers advise even wider separation — follow their instruction over this tool. (Well documented) |
| Phosphate binders (sevelamer, lanthanum) | Medications | Wait 4 hours after the dose | Bind levothyroxine in the gut. Keep them well away from the dose and monitor thyroid labs. (Reasonably documented) |
Most guidance is 30 to 60 minutes, and studies that measured absorption used espresso taken with or immediately after the tablet. Waiting a full hour is the safer default, and adding milk turns it into a calcium question, which needs about four hours.
Yes, many people do, and bedtime dosing performs at least as well as morning dosing in trials — provided it is roughly four hours after your last meal and away from calcium, iron and magnesium. What matters most is consistency, so pick one routine and keep it.
About four hours. Both bind levothyroxine in the gut and can noticeably reduce how much you absorb. The answer is separation, not avoidance — low ferritin is worth correcting if your labs show it.
No. Biotin does not affect absorption, but it can interfere with the lab assays used for TSH and free T4 and make results look misleading. The usual advice is to stop biotin at least 48 hours before a thyroid blood test, or tell the lab that you take it.
Generally no. Neither has a documented absorption interaction with levothyroxine on its own. The exception is a combined calcium and vitamin D tablet, which follows the calcium rule of four hours.
One imperfect day does not undo your treatment. Keep the rest of the week consistent rather than doubling a dose, and if your routine has genuinely changed, mention it before your next thyroid test so results are read in context.