Caffeine is the most ergogenic legal substance you can take during a race, and most ultrarunners use it wrong. Below: a working protocol with citations to mistake-types, not studies.

The pre-race dose

3 mg of caffeine per kg of body weight, 60 minutes before the start. For a 70 kg runner, that’s 210 mg — about two strong cups of coffee, or one tall coffee + a 100mg pill.

This dose hits peak blood concentration around mile 5–6 and gives you 4 hours of clear performance lift. The effect is real and well-documented: ~3% improvement in time-trial performance, lower perceived effort, better focus.

Common mistake: taking it with breakfast at 4 AM. By 6 AM start time, you’re already past peak. Time the dose 60 minutes before gun, not before breakfast.

The mid-race pulses

Around hour 4 and hour 8, take 100 mg caffeine pills (or a caffeinated gel). The race-day caffeine strategy is “build a baseline, pulse over time.”

The mistake here is taking too much too often. Caffeine doesn’t stack linearly — 4 doses of 100mg in 4 hours doesn’t produce 4× the effect, it produces jittery hands and an upset stomach. Spacing matters.

The back-half rescue

Around hour 16–18, when motivation is at its lowest, take 200 mg of caffeine + a Coke + a 50-calorie sugar source. This combination produces the biggest mental swing of the race — going from “I want to drop” to “I can finish” in 20 minutes.

The mistake here is using this as a strategy from the start. Caffeine + sugar combo loses effectiveness if you’ve been dosing all day. Save the big rescue dose for the late-race emergency.

When NOT to use caffeine

Sleep races (200-milers). A 100-miler caffeine plan is 3 doses across 24 hours. A 200-miler is different — you’ll need to sleep at hour 38, and high circulating caffeine prevents the sleep that prevents hallucinations. Cut caffeine the moment you plan to sleep; restart only after you’ve slept.

Cold races where you’ll be peeing constantly. Caffeine is a diuretic. In cold conditions, your bladder is already working overtime; adding caffeine produces a 30-second pee stop every 45 minutes. Cut caffeine to half-doses or skip entirely.

If you’re caffeine-naïve. Don’t introduce caffeine on race day. The “untrained” gut tolerates it poorly. Practice the protocol on at least three long training runs before you race it.

The form factor

  • Pills (NoDoz, ProPlus): $4 for 100, takes effect in 30 min. Cleanest delivery.
  • Caffeinated gels (Maurten 100 caf, GU Roctane): dual-purpose — calories + caffeine. Slower kinetics than pills (~45 min to peak).
  • Coke at aid stations: classic for a reason. ~30mg per 12 oz can, plus immediate sugar. Best for the back-half rescue.
  • Coffee: unreliable dosing. Strong morning coffee = 100–200 mg depending on prep. Fine for pre-race; avoid mid-race.

The honest caveat

A 3% performance improvement is real but not transformative. Caffeine is the smaller half of fueling; carbs and sodium are the larger half. Don’t over-rotate to caffeine and skimp on calories — that’s the fastest way to a hard bonk.

Used correctly, caffeine is the cheapest race-day improvement available. Used incorrectly, it’s the reason you’re peeing every 30 minutes at hour 14 and crashed by hour 16.