Frequently Asked Questions

CanIStackThis keeps one list of everything you take: prescriptions, supplements, and the coffee, energy drinks or grapefruit juice you have most days. Each supplement, food and drink is checked against the rest of the list, again every time the list changes. Two medications are checked against each other only where one of our rules covers that pair. What we could not check is named: any other medication pair is for your pharmacist, and anything on the list our rules do not cover is marked Not rated. A curated, hand-written interaction rule set decides every finding and its severity word (Major, Moderate or OK); no AI model decides a finding. The check is free and needs no account, and we don't sell supplements, run ads, or take affiliate commissions.

Yes, and it stays that way. We do not paywall safety information: somebody who pays nothing is shown every warning a subscriber is shown, at the same severity. Free, forever:

• The check, and every warning it finds
• Daily totals and limits across all your products
• My day, with spacing, and reminders with a free account
• Questions for your pharmacist, a printout for your doctor
• Your latest lab report, beside what you take, with a free account
• Your notes, the reasons you gave, and a page for each notes window, with a free account

Fair-use rate limits apply. A free account keeps your list on every device, with your conditions and your lab values beside it. Checking is free. Premium remembers. See the Premium page for what the paid tier adds.

The findings are decided by a hand-written rule set, not by an AI model: serotonergic pairs, blood thinners with bleeding-risk supplements, potassium with ACE inhibitors, thyroid and antibiotic mineral spacing, upper-limit overlap across products and more. Those rules can only make a result stricter. We do not have access to proprietary medical databases or clinical trial data, and a compound we haven't added yet gets no rule of its own: it is shown as Not rated, and the absence of a warning is not proof that a combination is fine. Two medications are checked against each other only where one of our rules covers that pair; any other medication pair is for your pharmacist, and the list says so. This is interaction information, not medical advice; check with your pharmacist or doctor before changing what you take.

Checking is free. Premium remembers.

• Free, forever: The check, and every warning it finds; Daily totals and limits across all your products; My day, with spacing, and reminders with a free account; Questions for your pharmacist, a printout for your doctor; Your latest lab report, beside what you take, with a free account; Your notes, the reasons you gave, and a page for each notes window, with a free account.
• Premium, $9.99 a month or $59 a year. Your history, your lab results from one report to the next, and DNA analysis while you subscribe.
  • History. What you took, when you stopped, what changed. Every change and every note on one dated printout, for dates you pick, up to one year apart. Two periods of your notes, side by side.
  • The watch. Re-checked when a rule or a result changes. We only message you when something did.Not switched on yet. The re-check runs today and stores the new verdict; we'll start sending the message when this is switched on.
  • Lab history, report to report.
  • DNA analysis while subscribed. A year also lets you download the report as a file you keep.
  The yearly plan bought on this website carries a 30-day money-back guarantee.
• DNA report, $29 once · or included with a year. Upload your 23andMe or AncestryDNA file. We read nine variants across seven genes and show where some of them touch the things on your list. The file is read in memory and never stored. The one-time report carries a 14-day money-back guarantee.

Cancel any time; you keep access to the end of the period. We don’t sell supplements. No ads, no affiliate links. We don’t sell your data. See the Premium page for full details.

DNA analysis that comes with a subscription stops being available when the subscription ends. First, what we actually store: we never keep your raw DNA file. It's read in memory and discarded immediately. We keep what was read from it (the variants we read and your genotype at each), the notes written from those results, the file's name and when you agreed to the upload, and you can delete all of it any time from your DNA report page. We keep those results until you delete them (nothing expires them on a timer), so subscribing again restores access to them. DNA analysis while subscribed. A year also lets you download the report as a file you keep. The DNA report on its own is $29 once, with no subscription needed. The one-time report carries a 14-day money-back guarantee: email hello@canistackthis.com within 14 days of purchase for a full refund (one refund per customer).

From four things, none of them a live feed off a third-party medical website:

• Our own interaction rule set, written and reviewed by hand
• The NIH Dietary Supplement Label Database, queried live over its public API for real product labels
• NIH Office of Dietary Supplements fact sheets, read by a human and distilled into our spacing, absorption, and upper-limit guidance (we link the fact sheet where we use it)
• A curated local knowledge base of 380 supplements plus 449 medication, drug and brand names that ships with the app

We do not have access to proprietary medical databases, clinical trial data, or official regulatory agency APIs. Checking every medication against every other needs a licensed drug compendium, so we check two medications against each other only where one of our rules covers that pair, and any other medication pair is for your pharmacist. See How We Score for the method and the exact size of every file behind it.

Every finding carries one of three severity words: Major, Moderate or OK. The hand-written rules set the severity for every pair they cover, and nothing downstream can lower it: the rules only ever add a finding or raise a severity, never remove one. A daily total that goes past an upper limit is shown with the limit beside it. The supplement pair guides also show a score from 1 to 10. That score comes from an AI-written analysis of the pair, not from these rules; our rules check it and can only make it stricter. The system errs toward caution.

Your list is checked again whenever it changes. The interaction rules and compound notes behind the check are a curated local knowledge base written by hand by us and reviewed periodically. We do not scrape or query third-party medical websites at request time. The one live external lookup is the NIH Dietary Supplement Label Database, which we query for product-label amounts. CanIStackThis is not a real-time clinical feed, so the information may not reflect the very latest research, so always confirm with a healthcare professional before making supplement decisions.

Put everything you take on your list: type it, paste a list, scan a label or say it. Each supplement, food and drink is checked against the rest of the list, and again whenever the list changes. Two medications are checked against each other only where one of our rules covers that pair; any other medication pair is for your pharmacist, and the list says so. To look at something new first, use Before you take it, which checks one thing against your list. Anything we hold no rule for is listed back to you by name as Not rated rather than quietly passed over. Silence is not a clearance.

Tell us through the contact form or email hello@canistackthis.com. Both land in the same inbox. Include the exact items you entered, which screen showed the problem, what you believe is wrong, and a source if you have one. A report that turns out to be right gets the file changed; one that turns out to be wrong gets an answer explaining why, not silence.

Yes. Signed out, your list is kept in this browser tab until you close it, and moves into your account when you sign in. With a free account it is kept on your account and follows you to every device, and every change you make to it is recorded. Everyone can see the three most recent changes. Seeing your whole history is part of Premium, $9.99 a month or $59 a year. The check, every warning, daily limits, spacing and My day stay free. See the Premium page.

Yes. We publish educational information that we write up ourselves from published research and public government fact sheets (NIH Office of Dietary Supplements and NCCIH monographs, prescribing information, and cited PMIDs), and most rules carry their source in the file beside them. It is interaction information, not medical advice, and it does not replace your doctor or pharmacist. Always consult a healthcare provider before making supplement decisions.

We collect minimal information necessary to provide our services, such as what you put on your list and basic analytics. The check works without an account. See our Privacy Policy for complete details on data collection and use, including the lab values you can choose to type in.

Companies can request corrections of factual inaccuracies, or send supporting documentation, through the contact form or hello@canistackthis.com. To be clear about what would be corrected: our analysis is not assembled from third-party medical websites. It comes from interaction rules and compound notes we write and maintain by hand in our own repository, plus one live lookup to the NIH Dietary Supplement Label Database for the amounts printed on a product label. A correction changes that source file, which changes what everyone sees.

Try refreshing the page or clearing your browser cache. If problems persist, contact our technical support at hello@canistackthis.com with details about your browser, device, and the specific issue you're experiencing.

CanIStackThis works in any phone browser with nothing to install, and it's also an installable web app: use your browser's "Add to Home Screen" and it opens like an app. Signed in, My day also gives you a calendar file that puts your times in your phone's calendar.

Not as a link yet. Your list has a “Print for my doctor” button, which uses your browser's print, and Before you take it can be printed the same way. Remember that supplement needs are personal: what works for one person may not be appropriate for another.