Interaction risk is the probability that two or more compounds in a planned stack will act on the same receptor, enzyme, or physiological system closely enough that their combined effect is larger, smaller, or qualitatively different from either compound alone. Unfair evaluates interaction risk at three moments — when a user adds an ingredient to the builder, when a prescription medication is logged, and when a review cycle flags an unexpected symptom cluster. A flagged interaction does not always mean stop; it means the default scheduling logic cannot assume the compounds are independent, and the stack needs a specific decision before activation.
Severity tiers and required action
Every flagged pair is placed into one of three severity tiers. The tier determines whether the stack can activate, activate with modification, or stay blocked until a clinician reviews it.
| Severity | What it describes | Required action in Unfair |
|---|---|---|
| Mild | Additive load without organ-system risk (caffeine + L-theanine, magnesium + zinc GI overlap) | Warning surfaced, stack activates, review at 14 days |
| Moderate | Meaningful pharmacodynamic overlap without life-threatening failure modes (two wake-promoting agents, two mild serotonergics, two GABAergics at bedtime) | Activation requires explicit confirmation, one compound is held for staggered introduction, re-screen in 72 hours |
| Severe | Same-pathway stacking with known adverse outcomes (SSRI + high-dose 5-HTP, warfarin + high-dose fish oil, MAOI + tyramine-containing extract) | Stack blocked, clinician review required before the confirmation gate clears |
Tiers are assigned from the pair, not from either compound in isolation. A 200 mg caffeine dose is mild alone and mild with L-theanine; it becomes moderate once a second stimulant is added to the same morning window.
Common overlap patterns
Three patterns account for most flagged pairs in the Unfair library. Each has a characteristic signature in the log and a specific mitigation path.
| Pattern | Typical ingredients involved | Dominant failure mode | First mitigation step |
|---|---|---|---|
| Stimulant stacking | Caffeine, yerba mate, green tea extract, theacrine, pre-workout formulas, nicotine | Resting HR and BP lift, sleep onset latency increase, afternoon rebound | Consolidate to one stimulant source in the morning window |
| Serotonergic overlap | 5-HTP, tryptophan, St. John's wort, SAMe, high-dose saffron, SSRI/SNRI prescriptions, MDMA or tramadol exposure | Agitation, sweating, clonus, tachycardia — early serotonin toxicity signs | Stop all non-prescribed serotonergics and confirm with prescriber before reintroduction |
| Anticoagulant stacking | High-dose fish oil, vitamin E >400 IU, ginkgo, garlic extract, nattokinase, curcumin piperine, warfarin or DOACs | Bruising, nosebleeds, prolonged bleeding from small cuts, GI bleeding | Hold all supplemental anticoagulants until INR or prescriber input is current |
Overlap patterns compound. A user on 400 mg caffeine from coffee plus a 200 mg yerba mate extract plus a pre-workout with 150 mg additional caffeine is carrying 750 mg of daily caffeine equivalents — well past the 400 mg general adult ceiling — before any other stimulant is considered. See duplicate ingredient risk for how the builder enumerates those hidden contributors. Related framing lives in supplement stack mistakes to avoid under the interaction checks section.
Escalation triggers
Five symptom clusters move a flag from "watch" to "stop now" regardless of the tier originally assigned.
- Chest pain, palpitations lasting more than a few minutes, or resting heart rate 15+ bpm above the user's baseline for more than an hour.
- Bleeding that is new, heavy, or slow to stop — including unusually heavy menstruation on a newly added anticoagulant-adjacent supplement.
- Clonus, rigidity, agitation with sweating and fever on any serotonergic pair — presume serotonin toxicity until ruled out.
- New confusion, severe headache, visual changes, or one-sided weakness.
- Yellowing of skin or sclera, dark urine, or persistent right-upper-quadrant pain on a contraindication-flagged hepatic stack.
Any of these triggers instructs Unfair to lock the stack, clear the next scheduled reminder, and prompt for an in-app clinician handoff note.
Screening cadence
Interaction risk is not a one-time check. Unfair re-screens after every prescription added, every dose increase above the prior plateau, and every new compound added to an already-running stack. A stack that passed screening in January can fail screening in April if the user started a new SSRI, because the library's serotonergic load is now additive to a prescription it previously did not know about.
Staggered introduction for moderate-tier pairs
When two compounds share a moderate-tier pair, the builder defaults to a staggered schedule rather than simultaneous activation. Compound A runs alone for 7–14 days. Compound B is introduced only after the log shows no symptom cluster attributable to A. This matters because if a user activates both at once and develops afternoon tachycardia, neither compound can be blamed cleanly, and both typically get dropped when only one was the culprit. The same rule applies when a prescription change is followed by a supplement change within 14 days — the supplement change is held until the prescription's own adjustment period closes.
How this appears in Unfair
The builder runs the interaction screen before the activation button unlocks. Severe tier pairs hold the stack in a blocked state with the clinician note template pre-filled. Moderate pairs surface a staggered schedule — one compound starts in week one, the second in week two — so a symptom cluster can be attributed to a specific addition rather than the pair. Mild pairs activate normally with a note on the review chart so the cycle analysis does not treat the compounds as independent.
Clinical safety note
Interaction risk screens in Unfair are based on public pharmacology references and the product library's ingredient metadata; they are not a substitute for a prescriber's review of a full medication list. Any escalation trigger above, any new prescription medication, and any pregnancy, surgery, or hepatic or renal diagnosis is a reason to pause the stack and involve a clinician before resuming.