Caffeine tracking
Everything we've written about caffeine, sleep, and tracking your intake
Caffeine is the most-consumed psychoactive substance on the planet. It's also one of the easiest to over-do without noticing — most people underestimate their daily intake by 30-50%. This is our hub for everything we've written about how caffeine actually works in your body, how to track it without obsessing, and how to time it so it doesn't wreck your sleep.
The science is well-settled: caffeine has a 5-hour half-life, blocks adenosine receptors, builds tolerance through receptor upregulation, and affects sleep architecture even when you fall asleep on time. Where the practical advice gets less clear is the day-to-day translation — what 200 mg actually looks like in real drinks, when to stop drinking caffeine before bed, how to taper without withdrawal, and how to think about caffeine during pregnancy or while breastfeeding.
We build SipNote — a local-first caffeine tracker for iPhone and Apple Watch — partly because no Western app handles Asian beverages well (boba, milk tea, oolong), and partly because all the existing options are subscription-based. The writing below is what we've learned researching, building, and using it.
The app
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May 15, 2026 · 8 min read
Why I built SipNote without a subscription
A solo iOS developer's take on why charging $2.99 once felt more honest than $5 a month — and what it cost.
May 16, 2026 · 2 min read
为什么我做了一个懂奶茶的咖啡因追踪 app，而且永不订阅
一个独立开发者为什么选择一次性 ¥18 而不是 $5/月 — 以及 8 个月做 SipNote 的取舍与代价。
May 17, 2026 · 7 min read
Caffeine half-life and sleep — when to stop drinking coffee
The science of how long caffeine stays in your body, why a 3pm latte can still hit you at 11pm, and a simple rule of thumb to protect your sleep.
May 17, 2026 · 3 min read
奶茶、咖啡、能量饮料咖啡因含量大全（中国常见品牌 2026）
喜茶、奈雪、瑞幸、库迪、CoCo、一点点、KFC、东方树叶……一杯到底有多少咖啡因？以及你能再喝多少不影响睡眠。
May 17, 2026 · 7 min read
The Apple Watch caffeine widget I actually want — and how SipNote built it
A first-class watchOS complication for caffeine isn't a checkbox feature. Here's what makes a watch glance useful, and what most caffeine apps get wrong.
May 17, 2026 · 2 min read
想戒咖啡？慢慢减比突然戒更有效——三周渐进方案
突然戒咖啡的人 80% 在第三天复喝。这篇讲为什么，以及一个真正能跑完的三周渐进减量方案。
May 17, 2026 · 9 min read
How much caffeine is safe during pregnancy? A clear guide for 2026
The 200 mg/day limit explained — what counts as 200 mg, why the third trimester is different, and how to track without obsessing.
How it compares to other tools
Reference data
Browse the caffeine content reference — 50+ popular drinks with their caffeine values, sleep timing, and daily-limit context.
Frequently asked questions
How is caffeine processed by the body?
Caffeine is absorbed within 45 minutes of consumption, peaks in your bloodstream around 1-2 hours, then metabolizes with a 5-hour half-life via liver enzymes (primarily CYP1A2). Genetic differences in CYP1A2 mean some people clear caffeine twice as fast as others — the so-called 'fast metabolizers.' Pregnancy, oral contraceptives, and certain medications can slow caffeine metabolism significantly.
How much caffeine is safe per day?
The FDA and EFSA consensus is up to 400 mg/day for healthy adults — roughly four 8oz cups of brewed coffee or two large Starbucks lattes. During pregnancy, the ACOG and NHS recommend staying under 200 mg/day. Adolescents (13-17) should stay under 100 mg/day. Under 12, caffeine is not recommended at all.
When should I stop drinking caffeine before bed?
The rule of thumb: stop 10 hours before your target bedtime if you want zero caffeine impact on sleep architecture, or 6 hours before if you're okay with some impact on deep sleep. For most people, that means cutting off caffeine by noon to 1pm if you want clean 10pm sleep.
How accurate are caffeine tracker apps?
Accuracy depends on the data source. Apps that auto-detect brand and size from a photo (like SipNote's on-device OCR) eliminate self-reporting error. Apps that require manual entry rely on you accurately picking the drink, which most people get wrong by ~30%. The body math (half-life decay, peak time) is well-established and consistent across apps; the input quality varies.