# Interaction Checker (interaction-checker.com)

> Free drug interaction checker. Every result quotes the FDA prescribing label sentence it came from, with a DailyMed link. Covers prescription and OTC drugs plus supplements, vitamins, foods, alcohol, tobacco, and cannabis. No account, no ads, no tracking; the medication list stays in the browser.

## Method
- Source: FDA prescribing labels via openFDA/DailyMed (public domain); NIH ODS, NCCIH, FDA, and NIAAA fact sheets for supplement/food/alcohol rules.
- Matching: whole-word search of each label's boxed warning, contraindications, warnings, and drug interactions sections for the other drug's name or drug class, in both directions.
- Severity: Major (boxed warning, contraindications, or wording such as contraindicated/avoid/not recommended), Moderate (monitor/dose/adjust wording), Minor (plain mention), No significant interaction (label explicitly reports none).

## Pages
- /                     The checker (client-side; supports ?d=id1,id2 links)
- /drugs                Drugs A to Z
- /drugs/<id>           Every documented interaction for one drug
- /drugs/<id>/pills     What the drug looks like: every tablet/capsule version in its FDA labels (imprint, color, shape, size, labeler) with rendered images
- /drugs/<id>/facts     Sourced facts, community claims with evidence status, common misconceptions, and FAQ (every line cites its source)
- /pills                Pill images by drug
- /supplements          Supplements, food, and alcohol
- /supplements/<id>     Every drug label mentioning that item, plus curated rules
- /interactions/<a>-and-<b>   One pair, all quotes, both labels
- /guide                How drug interactions work
- /guides               Reference guides on the label data: serotonin syndrome, opioids with benzodiazepines and other sedatives, QT prolongation, bleeding risk, alcohol, grapefruit, and the 2026 report on interaction warnings in FDA labels
- /guides/<slug>.md     Each guide as plain markdown, same words and numbers as the page
- /about                Method, sources, limits, data dates, FAQ
- /disclaimer           Medical disclaimer

## Languages
- Every page above except /disclaimer exists in English (no prefix) and under /fr /es /de /pt /pl /id /tr /ar /hi (for example /es/interactions/<a>-and-<b>). Slugs are the same in every language.
- Drug names are shown as each language writes them (paracetamol for acetaminophen outside the US). A label sentence shown in translation always has the English FDA original beside it; the English sentence is the evidence.

## Free API and MCP server (no key, no auth)
- /api                  Developer docs for the REST API
- /api/v1               API index (JSON): endpoints, limits, data dates
- /api/v1/openapi.json  OpenAPI 3.1 description
- /api/v1/checks?items=lisinopril,ibuprofen   Every pair among the items with severity and verbatim label quotes (GET or POST {"items":[...]})
- /api/v1/substances?q=advil                  Typo-tolerant search by name, brand, alias, class, or plain language
- /api/v1/substances/<id>                     One substance: names, classes, label source, interaction counts
- /api/v1/substances/<id>/interactions        Everything it interacts with, most severe first
- /api/v1/substances/<id>/pills               Tablet and capsule versions with image URLs
- /api/v1/substances/<id>/facts               Sourced facts, community claims with status, misconceptions, FAQ
- /mcp                  MCP server (Streamable HTTP, stateless) with tools check_interactions, search_substances, get_substance, get_substance_interactions, get_pill_appearances, get_drug_facts, and the ChatGPT connector pair search/fetch. Setup for each client at /mcp-server.
- Limits: 10 requests per minute per IP, 10 items per check. Need more? Request a higher limit at https://interaction-checker.com/api?request=higher-limits. Responses are cacheable for an hour. Link back to interaction-checker.com when showing results.

## Pill images
- Appearance data: DailyMed SPL product characteristics (SPLCOLOR, SPLSHAPE, SPLSIZE, SPLIMPRINT, SPLSCORE) per labeler.
- Images: renderings generated from those fields, not photographs; the imprint and proportions match the label. Served from img.interaction-checker.com; reuse with a link back.

## Community claims
- "What people say online" items are collected from public forums and review sites and shown next to primary-source evidence with a status (unproven, partly supported, disputed, debunked). They are not facts.

## Not medical advice
Severity reflects label wording, not an individual's situation. Absence of a documented interaction is not evidence of safety.