Interactions
Medications you should never mix: 12 dangerous combinations
The 12 prescription combinations that send people to the ER most often, the mechanisms behind each, and what to ask your pharmacist before refilling.
Plain-English pharmacy intelligence
Will any of your meds work against each other? Check in 5 seconds.
Most people on three or more prescriptions have at least one moderate or worse interaction. Your doctor's office software catches the obvious ones. We catch the rest, plus the food and supplement combos most pharmacists don't have time to flag.
600k+
Adults 65 and older end up in the ER more than 600,000 times a year for problems with their medications. That's roughly twice the rate for younger adults.
CDC FastStats, Medication Safety Data 2026. cdc.gov
Or jump straight to the tool
Check drug interactions in one second.
Severity-graded warnings sourced directly from openFDA. Patient assistance matching across 209 manufacturer databases. Insurance formulary lookup across 30+ plans. Free, private, no login.
Interaction Checker
Quick add:
+ lisinopril
+ ibuprofen
+ metformin
+ warfarin
+ sertraline
| Drug A | Drug B | Severity | Mechanism | Action |
|---|---|---|---|---|
| lisinopril 20mg | ibuprofen 800mg |
Major
Don't take together without calling your doctor today.
|
renal function decline + hyperkalemia risk Your kidneys could get strained and your potassium could climb to a dangerous level. | View → |
| lisinopril 20mg | atorvastatin 40mg |
Minor
Probably fine. Note it on your meds list.
|
no clinically significant effect documented No real conflict on record between these two. | View → |
| lisinopril 20mg | metformin 500mg |
No interaction
Safe combination. No action needed.
|
independent mechanisms, safe combination These two work in different ways and don't get in each other's way. | View → |
| lisinopril 20mg | potassium 99mg |
Moderate
Worth a 30-second mention at your next refill.
|
additive hyperkalemia, monitor K+ every 2 weeks Both push your potassium up. Ask your doctor about a blood test every two weeks. | View → |
What each severity means for you
Danger
Call your doctor today
Major interaction. Don't take these together until a prescriber has reviewed it. Don't stop either drug on your own first.
Caution
Mention at next visit
Moderate interaction. Usually manageable with a small dose change, timing change, or monitoring. Worth raising at your next appointment.
Monitor
Note it on your meds list
Minor interaction. Document it so the next clinician who treats you can see it. Usually no action required.
Safe
No action needed
No documented interaction. The two medications don't have a known mechanism that interferes with each other.
Data source
openFDA + NIH
Refresh cadence
Daily (automated)
Privacy posture
Browser-local only
Sponsored placements
Zero, ever
Common situations
Start with what brought you here.
"I'm starting a new medication."
Check it against everything else you already take, in 30 seconds.
Open interaction checker
"My prescription is too expensive."
Compare cash, GoodRx, and Cost Plus prices at pharmacies near you.
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"I can't afford my meds at any pharmacy."
209 manufacturer and nonprofit assistance programs, filtered by your income.
Find assistance you qualify for
"I take 5+ medications and I'm worried."
Add all of them at once. We'll flag every pairwise interaction and rank them by severity.
Run a full-stack check
"My doctor mentioned grapefruit."
50+ medications affected by grapefruit and the CYP3A4 mechanism, explained plainly.
Read the food-drug guide
"I'm on Medicare and confused about tiers."
See what your insurance covers, what tier each drug falls into, and what you'll actually pay.
Check your formulary
In 30 seconds
What OmniRx actually does.
12,400+
Drug interactions checked
Cross-referenced from FDA adverse-event data and DailyMed labels.
209
Assistance programs matched
Manufacturer, nonprofit, and federal programs filtered by your income.
30+
Insurance plans covered
Tier, copay, and prior-authorization flags for the plans most people are on.
0
Personal data stored
Everything runs in your browser. No accounts, no cookies, no medication list on our servers.
Every interaction, formulary, and program, mapped.
The full safety library behind The OmniRx Medication-Safety Standard, plus the open data.
Drug Interactions
FDA-sourced interaction profiles for the drugs people search most.
Formulary Coverage
Tier placement and copay estimates across major plans.
Patient Assistance
Manufacturer and nonprofit programs for expensive medications.
PBM Regulation by State
How pharmacy-benefit rules differ in all 50 states.
PBM & Drug Pricing Data
Our DOI-backed open dataset. Cite it, download it.
Free tools / no login
Six tools, one job: stay safe on your meds.
Drug Interaction Checker
Severity-graded warnings sourced directly from openFDA. Returns mechanism, clinical guidance, and safer alternatives.
FDA Safety Explorer
Search any prescription for FDA-reported adverse events, recalls, demographic risk patterns, and severity trends.
PAP Finder
Manufacturer-by-manufacturer eligibility logic across 209 active assistance programs. No signup required.
Insurance Formulary Checker
Check coverage and copays across 30+ plans. Find covered alternatives when your med isn’t listed.
My Medications
Browser-local drug list, never on our servers. Track interactions, get price alerts, FDA notification subscriptions.
Pharmacy Price Lookup
Cheapest pharmacy near you for any prescription. GoodRx and Cost Plus comparison via RxGrab partnership.
Methodology
Cited sources, timestamped refresh.
Every warning, profile, and eligibility check on OmniRx traces to a primary government or manufacturer source. We don’t paraphrase secondary sites. Refresh timestamps are visible on every page.
Our scoring and severity grading follows FDA classifications. We do not invent severity tiers or remix data into proprietary scoring. The output is the same data you would see on a clinician’s reference, formatted for consumer access.
Read methodology →| Source | Coverage | Last sync |
|---|---|---|
| openFDA | Adverse events (FAERS), drug labels | 6h ago |
| NIH | MedlinePlus consumer drug info | 12h ago |
| Mfr | 209 manufacturer PAP databases | 3d ago |
| RxGrab | Pharmacy price feed (sister site) | live |
Coverage
A reference library, not just a checker.
12,400+
Drug-pair pages
Each pair has its own page with severity, mechanism, clinical guidance, and alternatives.
209
PAP eligibility profiles
Manufacturer-by-manufacturer assistance program profiles with income thresholds.
200+
Drug safety profiles
FDA-sourced adverse-event summaries, recall history, demographic risk patterns.
Editorial standards ยท YMYL
Sourced from regulatory primaries.
OmniRx is a consumer intelligence platform, not a clinical service. Every drug-interaction page, severity grading, and patient-assistance eligibility logic is cross-cited from primary regulatory or peer-reviewed clinical sources before publication. We do not name a credentialed reviewer on any page unless that person is a contracted advisor whose review log we publish in full. Always confirm severity calls with your prescriber or pharmacist before changing or stopping any medication.
FDA
FDA + openFDA FAERS
REGULATORY PRIMARY
FDA Adverse Event Reporting System for severity grading; FDA Orange Book for therapeutic equivalence; openFDA labeling endpoints for prescribing information.
NIH
NIH + DailyMed + RxNorm
CLINICAL REFERENCE LAYER
DailyMed structured product labeling, RxNorm normalized drug nomenclature, NIH National Library of Medicine drug-interaction databases.
CMS
CMS + Manufacturer PAPs
ACCESS + COVERAGE
Medicare Part D plan-finder data; manufacturer patient-assistance-program eligibility criteria sourced from each program's public documentation.
Latest guides
Recent pharmacy intelligence articles
Pharmacy finance triangle.
OmniRx is the medication-intelligence node. Pair with sister sites for cost compare and supplement decisions.