Support
Questions? support@fizzlabs.ai — we reply within 1–2 days.
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Frequently asked questions
Is Jjan's guidance backed by science?
Yes. Everything Jjan shows you — the pace light, personalized hangover care, the liver recovery timer — is grounded in peer-reviewed medical research and trusted public health guidelines. A few highlights:
- Intoxication estimates: the Widmark equation · total body water (Watson 1980) · body-type distribution coefficients (Seidl 2000) · absorption rates by beverage type (Mitchell, ACER 2014) · drinking guidelines from the NIAAA and the Korea Disease Control and Prevention Agency.
- Liver recovery timer: based on published values for hepatic alcohol metabolism (zero-order kinetics — a steady breakdown rate per hour) and the elimination rate (β). More detail under "How is the liver recovery time calculated?" below.
- Hangover care: built on systematic reviews of hangover interventions (including BMJ 2005) and recent mechanism research — and we're honest about the evidence: reliable recovery comes down to time and rest.
Jjan doesn't inflate numbers or promise a "hangover cure" without evidence. When the evidence is weak, we say so — that's how we keep your trust. You'll find the research behind each feature on our Science page.
How is the light (green · yellow · red) determined?
We combine what you told us during onboarding — sex, age range, build, usual tolerance, and whether you flush when drinking — with the beverage type and timing of each drink you log. The formula was designed around figures from 16 medical papers and drinking guidelines from Korea and abroad — research like body-type alcohol distribution (Seidl 2000), total body water (Watson 1980), and absorption rates by beverage type (Mitchell 2014). That's why the same three drinks can move the light differently for different people and different drinks.
That said, it's an estimate and for reference only — never use it to decide whether you can drive.
Why don't you show a number (intoxication score)?
It's on purpose. Personal intoxication estimates are reference-grade accuracy, and showing a number creates the illusion of more precision than there really is. So Jjan speaks in just three lights — you're good (green), easing off (yellow), and that's it for tonight (red).
Do I have to sign in with Apple?
Yes. Jjan uses Sign in with Apple. An account is what keeps your history safe and carries it over when you switch phones. Your history is backed up only to your own iCloud — the developers can't see it. The only sign-in data we receive is the anonymous identifier Apple issues; nothing more.
I want to delete my history and account completely
"Delete account" (Profile > Account > Delete account) permanently deletes all your session and drink records, your baseline, and your recordings — including the iCloud backup on iPhone or the Google Drive backup on Android. This can't be undone. Subscriptions are separate from account deletion, so please cancel yours in iOS Settings > Subscriptions (iPhone) or Google Play > Payments & subscriptions (Android). What gets deleted, what stays, and how to delete without the app: account deletion guide.
I missed logging some drinks last night. Can I fix it?
Yes. Use "Fix My Log" below the morning report to add the drinks you missed, with beverage type and size.
The drink I usually have isn't in the list
Tap + on the drink button to choose from 19 beverage types with type-specific sizes (glass, bottle, can, shot, and more), or enter a custom volume in ml. The drinks you log most often sort to the front. If your drink still isn't there, let us know — we'll add it in an upcoming update.
The Quiet Exit (fake call) isn't ringing
Please check that notifications are on in iOS Settings > Jjan > Notifications, and that a Focus mode (Do Not Disturb) isn't blocking them. If the silent switch is on, it will only vibrate. The call audio plays through the earpiece only, so you have to hold the phone to your ear — the people next to you not hearing it is by design.
I'm seeing ads. Is that normal?
If you're not on Premium, a short rewarded ad plays when you start a session, and when you open a past record's details in the Records tab or open a morning report. Your first session starts ad-free, and Premium removes ads entirely. Jjan doesn't track you for personalized advertising, so any ads you see are non-personalized.
How much is Premium?
₩6,900 per month, ₩49,000 per year (first year 50% off worldwide: ₩24,500), or ₩129,000 for lifetime. The first-year annual discount is applied automatically at checkout. Premium unlocks ad removal · personalized hangover care · the liver recovery timer · voice packs · deeper insights · the Apple Watch app · all-time rhythm analysis.
What is personalized hangover care? (the evidence)
It's a Premium feature that shows a recovery guide tailored to that night's session in your morning report and session details. It's not the same advice every day — the care changes with how the night went:
- How much you drank — recovery priorities shift with intensity in standard drinks.
- How fast you drank — a high drinks-per-hour pace spikes acetaldehyde, worsening headache and nausea. After a fast night, hydration guidance gets emphasized.
- When you finished — drinking late (into the early hours) disrupts REM sleep, so even a long sleep doesn't feel refreshing. We'll suggest catching up, like a nap.
- Session length and setting — long sessions mean accumulated dehydration, and settings like work dinners, drinking solo, or a night with friends each add their own note.
Answer the morning condition check and, as your history builds, Jjan learns your personal pattern — like "past a certain number of drinks, my next day tends to be rough" — so it fits you better the more you use it.
The evidence: systematic reviews of hangover interventions (Pittler, Verster, Ernst, BMJ 2005; follow-up reviews 2017 and 2022) conclude there is no method with strong evidence for treating a hangover. The only reliable recovery is time and rest. Water, electrolytes, sleep, and easy-to-digest food can help relieve accompanying symptoms (weak-to-moderate evidence), and recent research finds water alone doesn't meaningfully reduce hangover severity (Utrecht, 2024). That's why Jjan never promises a "hangover cure" — only evidence-based relief and safety guidance. This is general wellness information, not medical advice. If there are emergency signs like repeated vomiting or reduced consciousness, call emergency services (119 in Korea) immediately.
How is the liver recovery time calculated? (the evidence)
The liver recovery timer shows the estimated time until your blood alcohol concentration (BAC) returns to zero after your last drink. It's calculated in two parts:
- How high it goes — the Widmark equation, adjusted with total body water (Watson 1980), body-type distribution coefficients (Seidl 2000), and absorption rates by beverage type, estimates your peak concentration based on sex, age, height, and weight.
- How fast it comes down — about 90% of alcohol is broken down in the liver by enzymes (ADH and ALDH). These enzymes saturate even at low concentrations, so alcohol is eliminated at a nearly constant rate per hour (zero-order kinetics). That means BAC falls in a straight line, and the app uses a conservative elimination rate within the published range (roughly 0.012–0.020% per hour). Where that line hits zero is when your liver "clocks out."
As your history builds, this time gradually adjusts to your personal metabolism (with a safety cap on how far it can adjust). Still, metabolism varies widely with genetics, food, and how you're doing that day — this is an estimate only, and must never be used for medical or driving decisions.
References: the Widmark equation · Watson TBW (1980) · Seidl (2000) · zero-order alcohol metabolism (ADH/ALDH) · NIAAA.
I want to switch plans (monthly ↔ annual)
On the Premium screen in your profile, tap "Change Plan · Manage Subscription" to open Apple's subscription management sheet. From there you can switch between monthly and annual (upgrade or downgrade); per Apple's rules, the change takes effect at your next billing cycle. You can reach the same screen via iOS Settings > your name > Subscriptions.
I want to cancel my subscription
Subscriptions are managed by Apple. You can cancel anytime via Profile > Premium > "Change Plan · Manage Subscription", or in iOS Settings > your name > Subscriptions. After canceling, Premium stays active for the rest of your paid period.
Requests and ideas
New beverage types, voice pack ideas, translation suggestions — send anything to support@fizzlabs.ai. We're also on Instagram, TikTok, and X at @jjan_app.