The Science

Jjan's guidance is grounded in peer-reviewed medical research and trusted public health guidelines. When the evidence is strong we say so, and when it's weak we say that too — that's how we keep your trust. This app is not a medical service and must never be used to decide whether you can drive.

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The intoxication engine

From the drinks you log — beverage type, amount, and timing — plus your sex, age, height, weight, usual tolerance, and whether you flush when drinking, Jjan estimates an intoxication curve calibrated to your body.

• The Widmark equation — the classic model for estimating blood alcohol concentration.
• Total body water (TBW) — Watson et al., 1980. Distribution volume from sex, age, height, and weight.
• Distribution coefficient r — Seidl et al., Int J Legal Med 2000. Regression equations by body type.
• Absorption rates by beverage type — Mitchell et al., Alcohol Clin Exp Res 2014.
• Drinking guidelines — NIAAA (binge drinking definition) · Korea Disease Control and Prevention Agency · Korea's Road Traffic Act §44 as anchors.

Why show three lights (green · yellow · red) instead of a number? Because personal intoxication estimates are "reference-grade" accuracy. A number creates the illusion of more precision than there really is.

Liver recovery timer

After a session ends, this shows the estimated time remaining until your liver has fully broken down the alcohol — the point when your estimated blood alcohol concentration (BAC) returns to zero after your last drink.

• Zero-order kinetics — about 90% of alcohol is metabolized in the liver by enzymes (ADH and ALDH). These enzymes saturate even at low concentrations, so alcohol breaks down at a nearly constant rate per hour. That's why BAC falls in a straight line.
• Elimination rate (β) — the published range is roughly 0.012–0.020% per hour. Jjan defaults to a conservative value and, as your history builds, adjusts toward your personal metabolism — with a safety cap on how far it can adjust.

Metabolism varies widely with genetics, food, how you're doing that day, and liver health. These are estimates only, and can't be used for medical or driving decisions.

Personalized hangover care

A recovery guide tailored to how much you drank last night and how you feel this morning. As your history builds, it also learns your personal hangover pattern.

• Systematic reviews — Pittler, Verster, Ernst, BMJ 2005; follow-up reviews 2017 and 2022. The shared conclusion: there is no method with strong evidence for treating a hangover. The only reliable recovery is time and rest.
• The limits of hydration — water alone doesn't meaningfully reduce hangover severity (Utrecht, 2024). Water, electrolytes, sleep, and food help relieve accompanying symptoms (weak-to-moderate evidence).
• Safety — repeated vomiting or reduced consciousness isn't a hangover; it suggests acute alcohol poisoning → call emergency services (119 in Korea) immediately (NIAAA · Cleveland Clinic). Excess acetaminophen (Tylenol) after drinking risks liver toxicity.

That's why Jjan never promises a "hangover cure." We only offer evidence-based relief and safety guidance, honestly.

Key references

• Watson PE, et al. Total body water volumes for adult males and females. Am J Clin Nutr 1980.
• Seidl S, et al. The calculation of blood ethanol concentrations. Int J Legal Med 2000.
• Mitchell MC, et al. Absorption and peak BAC by beverage type. Alcohol Clin Exp Res 2014.
• Pittler MH, Verster JC, Ernst E. Interventions for preventing or treating alcohol hangover. BMJ 2005;331:1515.
• Alcohol hangover versus dehydration revisited (Utrecht), ScienceDirect 2024.
• NIAAA — Understanding the Dangers of Alcohol Overdose.

Curious about the full reference list and evidence grades? Ask us at support@fizzlabs.ai.