Medication Safety

How to check a medication and supplement interaction

Use the checker to select the specific medication and supplement (or two medications) you want to check. If a reviewed record exists for that pair, you will see its classification (avoid, use caution, monitor, or informational), the evidence behind it, and any timing consideration. If no reviewed record exists yet, the checker says so directly rather than implying safety.

Warfarin and supplements

Warfarin is one of the most interaction-sensitive medications in common use, because its effect (blood clotting time) is narrow-margin and easily shifted. Our reviewed catalog documents interactions between warfarin and sertraline (increased bleeding-risk, named directly on warfarin's own label) and omeprazole (increased INR, described on omeprazole's label), plus a mixed-evidence finding with turmeric. Never stop or adjust warfarin based on this site -- INR monitoring and dose changes need a clinician.

Levothyroxine and supplements

Levothyroxine absorption is well documented to be sensitive to timing around certain minerals and foods. Our catalog includes reviewed spacing considerations involving levothyroxine, including monitor-level interaction findings with omeprazole and sertraline -- see Timing & Absorption for the specific windows on record.

Antibiotics and mineral supplements

Tetracycline-class antibiotics (including doxycycline in our catalog) are well documented to have reduced absorption when taken close to certain mineral supplements, such as zinc, calcium, iron, or magnesium. This is a timing issue more than an avoidance issue in most cases -- see Timing & Absorption for the reviewed separation window.

Blood pressure medicines and supplements

Potassium-sparing blood pressure medications, such as spironolactone, can raise potassium levels -- combining them with potassium supplements, or with an ACE inhibitor like lisinopril (which itself can raise potassium), compounds that risk. This is a real, high-evidence, named finding in our catalog.

What interaction warnings mean: avoid vs. monitor

These labels describe the strength and nature of the documented concern, not a single universal risk score:

• Avoid: sources document a clinically significant reason these generally should not be combined without a clinician's guidance.
• Use caution: a real interaction is documented that warrants care -- dose adjustment, spacing, or professional input.
• Monitor: a documented interaction worth watching for -- a lab value or symptom to keep an eye on while combining.
• Informational / no documented interaction identified: no clinically significant concern was found in the sources checked for this specific pair.

See Important Interactions for every currently reviewed avoid/caution/monitor pair, and the methodology page for how these classifications are assigned.

This site does not provide individualized medication-change instructions. Always follow your prescription label and talk to a pharmacist or clinician before starting, stopping, or adjusting a prescribed medication -- see the medical disclaimer.