Levothyroxine
Levothyroxine replaces endogenous thyroid hormone (thyroxine), undergoing peripheral deiodination into active liothyronine (T3) to regulate cellular basal metabolic rates.
Kitchen Food, Drink & Dietary Conflicts
Biochemical interactions with common foods, beverages & cooking ingredientsSome foods and beverages, particularly those that contain soybeans, walnuts, and dietary fiber, may affect how levothyroxine works for you. Talk to your doctor before eating or drinking these foods. Talk to your doctor about eating grapefruit and drinking grapefruit juice while taking this medication.
Grapefruit / Pomelo (Citrus paradisi / Citrus maxima)
Destroys enterocyte CYP3A4 enzymes, collapsing first-pass drug metabolism and causing up to 12-fold spikes in bioavailability for oral CYP3A4 substrates (statins, calcium channel blockers, immunosuppressants, PDE5 inhibitors).
Coffee & High-Caffeine Beverages (Espresso, Energy Drinks)
Ciprofloxacin, fluvoxamine, and oral contraceptives inhibit CYP1A2, reducing caffeine clearance by 30-80% and precipitating palpitations, panic, and severe tremors. Caffeine also accelerates gastric motility, impairing bisphosphonate and thyroid absorption.
Dairy Milk, Yogurt & Calcium-Enriched Foods
Divalent calcium binds fluoroquinolone (ciprofloxacin) and tetracycline (doxycycline) antibiotics into unabsorbable ring complexes, reducing systemic antibacterial coverage by up to 90% and causing therapy failure.
Fresh Orange Juice & Apple Juice (OATP Influx Blockers)
Unlike CYP3A4 inhibitors that increase drug levels, fruit juice bioflavonoids block the enterocyte OATP influx pumps, plummeting absorption of oral fexofenadine (Allegra), ciprofloxacin, and atenolol by 30-70%.
Prescription & OTC Drug Interactions (DDI)
Documented pharmacological conflicts & contraindicated co-prescriptionsDietary Supplements, Herbs & Minerals (DNI)
Interactions with over-the-counter vitamins, minerals, and herbal preparationsCalcium, Iron, Magnesium & Zinc Mineral Supplements
Polyvalent metal ions bind the medication into insoluble ring chelates in the gastrointestinal tract, dropping oral absorption by 50% to 90% and causing therapy failure.
Chronotherapy & Meal Administration Protocols
Optimal absorption, meal-timing rules & GI tolerability protocolsIt usually is taken once a day on an empty stomach, 30 minutes to 1 hour before breakfast.
Rationale: Food constituents interfere with gastrointestinal absorption or gastric emptying.
Take the tablets with a full glass of water as they may get stuck in your throat or cause choking or gagging.
Rationale: Promotes optimal mucosal absorption and consistent therapeutic plasma levels.
Only mix the crushed tablets with water; do not mix it with food or soybean infant formula.
Rationale: Food enhances bioavailability, prevents gastric mucosal irritation, or stabilizes peak-to-trough pharmacokinetic variations.
Frequently Researched Drug-Substance Combinations
Explore pairwise interaction dossiers and laboratory safety analysesLevothyroxine and Calcium
Pairwise Clinical Analysis & Safety RatingLevothyroxine and Iron
Pairwise Clinical Analysis & Safety RatingLevothyroxine and Coffee
Pairwise Clinical Analysis & Safety RatingLevothyroxine and Ashwagandha
Pairwise Clinical Analysis & Safety RatingLevothyroxine and Grapefruit
Pairwise Clinical Analysis & Safety RatingLevothyroxine and Grapefruit-juice
Pairwise Clinical Analysis & Safety RatingTaking Levothyroxine alongside daily coffee, supplements, or other medications?
Add all your daily medications, foods (Dairy, Spinach, Coffee, Grapefruit), and botanicals (Ashwagandha, Curcumin, Melatonin) into the SafeStack interactive engine to run full multi-way synergy collision analysis in real time.
Data on this clinical monograph is compiled from the U.S. National Library of Medicine (MedlinePlus), openFDA Structured Product Labeling (SPL Section 7 Drug Interactions), the NIH Office of Dietary Supplements (ODS), and Krause and Mahan's Food & Nutrition Care Process.