Meta Information
ID:levothyroxine
Name:
Schema Version:AIM-2.0
Interactions
Target id:
/dietary/meal
Target name:
Any Caloric Food or Meal
Severity:
major
Interaction type:
diminishing
Nature:
temporal
Temporal spacing:
Hours before target:
1
Hours after target:
4
Description:
Food, especially fiber and fats, can significantly bind to levothyroxine in the gut and reduce its absorption by up to 40%.
Actionable advice:
Take levothyroxine on an empty stomach, at least 60 minutes before eating or 4 hours after your last meal.
New description:
Food can bind to levothyroxine in your gut, significantly reducing its absorption. To ensure proper uptake, take your dose on an empty stomach at least 1 hour before eating or 4 hours after your last meal.
Target id:
/class/chelating-minerals
Target name:
Chelating Minerals (Calcium, Iron, Magnesium, Zinc, etc.)
Severity:
major
Interaction type:
diminishing
Nature:
temporal
Temporal spacing:
Hours before target:
4
Hours after target:
4
Description:
Multivalent cations (such as calcium, iron, magnesium, and zinc) bind directly to levothyroxine in the gut, forming a non-absorbable chelation complex that prevents its absorption.
Actionable advice:
Separate your levothyroxine dose from any mineral supplements by at least 4 hours.
New description:
Minerals like calcium, iron, and magnesium can bind to levothyroxine in the gut, preventing its absorption. You should take your dose at least 4 hours before or 4 hours after taking any of these mineral supplements.
Target id:
/class/antacids
Target name:
Multivalent Cation Antacids
Severity:
major
Interaction type:
diminishing
Nature:
temporal
Temporal spacing:
Hours before target:
4
Hours after target:
4
Description:
Antacids containing aluminum, magnesium, or calcium bind to levothyroxine in the gut, significantly reducing its absorption into the bloodstream.
Actionable advice:
Separate your levothyroxine and antacid doses by at least 4 hours.
New description:
Antacids with aluminum, magnesium, or calcium can bind to levothyroxine and block its absorption. Be sure to take your thyroid medication at least 4 hours before or 4 hours after taking an antacid.
Target id:
/class/bile-acid-sequestrants
Target name:
Bile Acid Sequestrants & Binders
Severity:
major
Interaction type:
diminishing
Nature:
temporal
Temporal spacing:
Hours before target:
4
Hours after target:
4
Description:
Drugs like cholestyramine and colestipol are designed to bind substances in the gut and will bind to levothyroxine, preventing its absorption.
Actionable advice:
Take levothyroxine at least 4 hours before or after taking a bile acid sequestrant.
New description:
Bile acid sequestrants are designed to bind substances in the gut and will also bind to levothyroxine, preventing its absorption. Take your levothyroxine dose at least 4 hours before or 4 hours after taking these medications.
Target id:
/intervention/vitamin-b7
Target name:
Biotin (Vitamin B7) Supplements
Severity:
major
Interaction type:
assay_interference
Nature:
temporal
Temporal spacing:
Hours before target:
72
Hours after target:
null
Description:
High doses of biotin interfere with the laboratory assays used to measure TSH and thyroid hormones, leading to falsely high or low results that can cause incorrect dosing.
Actionable advice:
Stop taking any supplements containing biotin for at least 3 days before having your thyroid function tested.
New description:
High-dose biotin can interfere with the lab tests used to measure thyroid hormones, leading to inaccurate results. To avoid this, stop taking biotin supplements at least 72 hours before your blood draw.
Target id:
/biomarker/thyroid-panel
Target name:
Thyroid Panel Blood Draw
Severity:
major
Interaction type:
assay_interference
Nature:
temporal
Temporal spacing:
Hours before target:
null
Hours after target:
1
Description:
Taking levothyroxine right before a blood test can cause a temporary, artificial spike in T4 levels, which may not reflect your true, steady-state hormone status.
Actionable advice:
On the day of your thyroid lab test, take your levothyroxine dose *after* your blood has been drawn.
New description:
Taking your dose right before a blood test can cause an artificial spike in T4 levels, which doesn't reflect your true baseline. On the day of your lab test, wait to take your levothyroxine until after your blood has been drawn.
Target id:
/intervention/warfarin
Target name:
Warfarin
Severity:
major
Interaction type:
adverse
Nature:
absolute
Temporal spacing:
null
Description:
Levothyroxine increases the body's breakdown of vitamin K-dependent clotting factors, which enhances the blood-thinning effect of warfarin and increases bleeding risk.
Actionable advice:
Monitor your INR closely when starting or changing your levothyroxine dose, as your warfarin dose may need adjustment.
New description:
Levothyroxine can enhance the effect of warfarin by increasing the breakdown of clotting factors, which raises bleeding risk. Your doctor will need to monitor your INR closely and may need to adjust your warfarin dose when starting or changing your thyroid medication.
Target id:
/condition/pregnancy
Target name:
Pregnancy
Severity:
major
Interaction type:
diminishing
Nature:
absolute
Temporal spacing:
null
Description:
Pregnancy significantly increases the body's demand for thyroid hormone, requiring a dose increase to support both maternal and fetal health.
Actionable advice:
Your levothyroxine dose will likely need to be increased by 30-50%; work closely with your doctor for frequent monitoring.
New description:
Pregnancy increases your body's demand for thyroid hormone to support both you and the fetus. Your levothyroxine dose will likely need to be increased, so it's critical to work with your doctor for frequent monitoring.
Target id:
/class/proton-pump-inhibitors
Target name:
Proton Pump Inhibitors
Severity:
moderate
Interaction type:
diminishing
Nature:
absolute
Temporal spacing:
null
Description:
These drugs reduce stomach acid, which is necessary for dissolving and absorbing the levothyroxine tablet, potentially leading to lower hormone levels over time.
Actionable advice:
Your levothyroxine dose may need to be increased; monitor thyroid function tests (TSH) closely with your doctor.
New description:
Proton pump inhibitors reduce stomach acid, which is needed to properly absorb levothyroxine from its tablet form. If you take these drugs, your doctor may need to increase your dose and should monitor your TSH levels.
Target id:
/dietary/caffeinated-beverages
Target name:
Coffee and Espresso
Severity:
moderate
Interaction type:
diminishing
Nature:
temporal
Temporal spacing:
Hours before target:
1
Hours after target:
1
Description:
Coffee can reduce the absorption of levothyroxine by altering gut transit time and potentially binding to the drug, even when separated by 30-60 minutes.
Actionable advice:
Wait at least 60 minutes after taking levothyroxine before drinking coffee.
New description:
Coffee can interfere with levothyroxine absorption by affecting gut transit time. To prevent this interaction, you should wait at least 60 minutes after taking your medication before drinking coffee.
Target id:
/dietary/soy-products
Target name:
Soy Products (Milk, Protein, Isoflavones)
Severity:
moderate
Interaction type:
diminishing
Nature:
temporal
Temporal spacing:
Hours before target:
4
Hours after target:
4
Description:
Soy proteins and isoflavones can interfere with the absorption of levothyroxine from the intestine.
Actionable advice:
Separate consumption of soy products from your levothyroxine dose by at least 4 hours.
New description:
Soy proteins can interfere with the absorption of levothyroxine in your gut. Avoid consuming soy products for at least 4 hours before and 4 hours after taking your dose.
Target id:
/class/anticonvulsants
Target name:
Enzyme-Inducing Anticonvulsant Medications
Severity:
moderate
Interaction type:
diminishing
Nature:
absolute
Temporal spacing:
null
Description:
Medications like phenytoin and carbamazepine speed up the liver's breakdown of levothyroxine, which can lower its levels and effectiveness.
Actionable advice:
Your levothyroxine dose may need to be increased; monitor TSH levels when starting or stopping these drugs.
New description:
Certain anticonvulsant drugs cause your liver to break down levothyroxine more quickly, reducing its effectiveness. Your doctor may need to increase your dose and should monitor your TSH when starting or stopping these medications.
Target id:
/class/estrogens
Target name:
Estrogens and Progestins (Hormonal Therapy & Contraceptives)
Severity:
moderate
Interaction type:
diminishing
Nature:
absolute
Temporal spacing:
null
Description:
Estrogens increase levels of thyroid-binding globulin (TBG), a protein that binds to thyroid hormone, reducing the amount of free, active hormone available to your cells.
Actionable advice:
Your levothyroxine dose may need adjustment when starting, stopping, or changing your estrogen dose; monitor TSH.
New description:
Estrogen increases a protein that binds to thyroid hormone, which reduces the amount of free, active hormone in your system. Your levothyroxine dose may need to be adjusted when you start, stop, or change your estrogen therapy.
Target id:
/class/antidiabetic-medications
Target name:
Diabetes Medications
Severity:
moderate
Interaction type:
adverse
Nature:
absolute
Temporal spacing:
null
Description:
Initiating thyroid hormone therapy can raise blood glucose levels, potentially reducing the effectiveness of your diabetes medication.
Actionable advice:
Monitor blood glucose closely when your thyroid dose changes, as your diabetes medication may need adjustment.
New description:
Starting or changing your levothyroxine dose can raise blood sugar levels, making your diabetes medication less effective. You should monitor your blood glucose closely during these times, as your diabetes medication may need to be adjusted.
Target id:
/circadian/wake
Target name:
Waking Up
Severity:
moderate
Interaction type:
requirement
Nature:
temporal
Temporal spacing:
Hours before target:
null
Hours after target:
0.5
Description:
Taking levothyroxine upon waking on an empty stomach is the most reliable way to ensure consistent, optimal absorption and aligns with the body's natural hormonal rhythms.
Actionable advice:
Take your dose with a full glass of water immediately upon waking.
New description:
Taking levothyroxine first thing in the morning on an empty stomach ensures consistent absorption and aligns with your body's natural rhythms. For best results, take your dose with a full glass of water as soon as you wake up.
Target id:
/circadian/sleep
Target name:
Going to Sleep
Severity:
moderate
Interaction type:
synergistic
Nature:
temporal
Temporal spacing:
Hours before target:
0.5
Hours after target:
null
Description:
Taking levothyroxine at bedtime, long after your last meal, is an effective alternative that may improve absorption for some individuals by ensuring an empty stomach.
Actionable advice:
If taking at night, ensure it is at least 4 hours after your last food intake.
New description:
Taking levothyroxine at bedtime can be an effective alternative, as it guarantees an empty stomach for better absorption. If you choose this timing, be sure to take your dose at least 4 hours after your last meal.
Target id:
/class/tricyclic-antidepressants
Target name:
Tricyclic Antidepressants
Severity:
moderate
Interaction type:
adverse
Nature:
absolute
Temporal spacing:
null
Description:
The effects of both levothyroxine and tricyclic antidepressants can be enhanced, potentially leading to cardiac arrhythmias or CNS stimulation.
Actionable advice:
Use with caution and report any heart palpitations or nervousness to your doctor.
New description:
Levothyroxine and tricyclic antidepressants can mutually enhance their effects, potentially causing heart rhythm issues or nervous system overstimulation. Use this combination with caution and report any palpitations or unusual nervousness to your doctor.
Target id:
/intervention/orlistat
Target name:
Orlistat
Severity:
moderate
Interaction type:
diminishing
Nature:
temporal
Temporal spacing:
Hours before target:
4
Hours after target:
4
Description:
The weight-loss drug Orlistat works by blocking fat absorption, but it can also bind to levothyroxine and prevent its absorption.
Actionable advice:
Separate your levothyroxine and Orlistat doses by at least 4 hours.
New description:
The weight-loss drug Orlistat can bind to levothyroxine in the gut, preventing it from being absorbed properly. You should take your thyroid medication at least 4 hours before or 4 hours after your Orlistat dose.
Target id:
/dietary/high-fiber-meal
Target name:
High-Fiber Meal
Severity:
moderate
Interaction type:
diminishing
Nature:
temporal
Temporal spacing:
Hours before target:
1
Hours after target:
4
Description:
High amounts of dietary fiber, such as from psyllium husk or cotton seed meal, can bind to levothyroxine and decrease its absorption.
Actionable advice:
Avoid taking levothyroxine with high-fiber meals or supplements; separate by at least 4 hours.
New description:
Large amounts of dietary fiber can bind to levothyroxine in the gut and reduce its absorption. Avoid taking your dose with high-fiber meals or supplements, separating them by at least 4 hours.
Target id:
/intervention/raloxifene
Target name:
Raloxifene
Severity:
minor
Interaction type:
diminishing
Nature:
absolute
Temporal spacing:
null
Description:
This selective estrogen receptor modulator (SERM) may decrease the absorption of levothyroxine, though the clinical significance is often minor.
Actionable advice:
Monitor TSH levels if you start or stop taking Raloxifene.
New description:
Raloxifene may slightly decrease the absorption of levothyroxine from the gut. Your doctor should monitor your TSH levels if you start or stop taking this medication to see if a dose adjustment is needed.
Target id:
/dietary/walnuts
Target name:
Walnuts
Severity:
minor
Interaction type:
diminishing
Nature:
temporal
Temporal spacing:
Hours before target:
1
Hours after target:
4
Description:
Walnuts have been specifically reported to interfere with the absorption of levothyroxine from the gut.
Actionable advice:
Avoid eating walnuts around the time you take your levothyroxine dose.
New description:
Walnuts contain compounds that can interfere with the absorption of levothyroxine in the intestine. It's best to avoid eating walnuts for at least 1 hour before and 4 hours after taking your medication.
Target id:
/dietary/grapefruit-pomelo
Target name:
Grapefruit Juice
Severity:
minor
Interaction type:
diminishing
Nature:
temporal
Temporal spacing:
Hours before target:
4
Hours after target:
4
Description:
Grapefruit juice can delay the absorption of levothyroxine from the intestine, potentially affecting its peak concentration.
Actionable advice:
It is best to separate your levothyroxine dose from grapefruit juice consumption by several hours.
New description:
Grapefruit juice can delay the absorption of levothyroxine, which may reduce its overall effectiveness. You should separate your dose from grapefruit juice consumption by at least 4 hours on either side.