Is it true that eating rice within an hour of taking levothyroxine reduces its absorption?

Short Answer

Eating rice itself has not been specifically shown to reduce levothyroxine absorption, but taking levothyroxine with any meal within an hour rice included can lower and make absorption more variable. This is because food in general, and especially foods high in dietary fiber or soy, can interfere with levothyroxine uptake; guidelines recommend taking levothyroxine on an empty stomach 30–60 minutes before breakfast. ^{[1] [2]} Food intake has been demonstrated to decrease levothyroxine absorption and raise TSH compared with fasting dosing. ^{[3] [4]}

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Why Timing Matters

• Empty stomach improves absorption: Levothyroxine is best absorbed when the stomach is empty and gastric acidity is optimal. Official dosing instructions advise taking it as a single daily dose on an empty stomach, 30–60 minutes before breakfast, with a full glass of water. ^{[1] [2]}
• Food lowers bioavailability: Clinical studies show that taking levothyroxine with food reduces absorption and results in higher, more variable TSH levels compared to fasting administration, indicating less consistent thyroid hormone exposure. ^{[3] [4]}

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Foods Known to Interfere

• Dietary fiber: Fiber can bind levothyroxine in the gut and reduce absorption. ^{[5] [6]}
• Soy products: Soybean flour and other soy foods are repeatedly noted to decrease absorption. ^{[5] [6]}
• Grapefruit juice: It can delay absorption and reduce bioavailability. ^[5]
• Coffee (espresso): Coffee has been reported to interfere with levothyroxine absorption, particularly when taken close to the dose. ^[7]

Rice itself is not singled out in official labeling as an interfering food; however, any meal especially if fibrous or combined with interfering items can reduce absorption if taken within an hour of the dose. ^{[1] [4]}

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Practical Dosing Tips

• Take levothyroxine first thing in the morning: Aim for 30–60 minutes before any food or drink other than water. ^{[1] [2]}
• Separate from binders: Keep at least 4 hours between levothyroxine and agents that bind it (e.g., calcium, iron, certain antacids). ^[1]
• Be consistent: If you must take it with food due to lifestyle, try to keep the routine exactly the same every day and work with your clinician to adjust the dose based on TSH trends, since non‑fasting dosing typically requires adjustments. ^{[2] [4]}

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Evidence Summary

• Labeling guidance: Emphasizes empty‑stomach dosing and cautions about foods (soy, fiber, walnuts, grapefruit juice) that can decrease or delay absorption. ^{[5] [1]}
• Human studies: Show significantly better absorption and tighter TSH control when levothyroxine is taken fasting compared with with breakfast or at bedtime. ^{[3] [4]}

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Bottom Line

While rice itself is not specifically identified as a problem food, taking levothyroxine within an hour of eating rice (or any meal) can reasonably be expected to reduce or vary absorption, and best practice is to take it on an empty stomach 30–60 minutes before breakfast with water. ^{[1] [4]}