How Much Caffeine Before a Marathon or Half Marathon?
I Am GroundedQuick answer
Most research supports 2–3 mg of caffeine per kg of body weight, taken about 60 minutes before the start. For a 70 kg runner that's roughly 140–210 mg. The Australian Institute of Sport notes that benefits plateau at around 3 mg/kg (about 200 mg), so more isn't better. Practise your plan on long training runs before race day.
Want your own numbers? Use our caffeine calculator to get a timed plan for your weight, sport and session.
Why do runners use caffeine?
Caffeine makes the same pace feel easier. The International Society of Sports Nutrition (ISSN) found aerobic endurance shows the most consistent benefit from caffeine, with doses of 3–6 mg/kg improving performance and benefits seen from as low as 2 mg/kg. The AIS recommends using the lowest dose that works for you, at around 2–3 mg/kg.
How do I work out my dose?
Multiply your body weight in kg by 2 to 3:
| Body weight | 2 mg/kg | 3 mg/kg |
|---|---|---|
| 55 kg | 110 mg | 165 mg |
| 65 kg | 130 mg | 195 mg |
| 75 kg | 150 mg | 225 mg |
| 85 kg | 170 mg | 255 mg |
The AIS fact sheet gives a safe ceiling for adults of no more than 200 mg in one sitting and 400 mg across the day from all sources, including your morning coffee. If your number is above 200 mg, split it: some before the start and the rest during the race.
When should I take caffeine before a marathon?
- 60 minutes before the gun: the most common timing in the research. Your pre-race coffee or a 60 mg Espresso SUPR Bar with breakfast fits here.
- Mid-race top-up: in a marathon, a second smaller dose around halfway (roughly 18–25 km) helps when fatigue starts to build.
- Half marathon: most runners only need the pre-race dose. Faster runners finishing under 90 minutes rarely need a top-up.
Does the caffeine source matter?
ISSN notes the best timing depends on the source, and that gels, chews and gum have all improved aerobic performance. What matters most is knowing exactly how much you're taking. Café coffee varies hugely: the AIS lists brewed coffee at about 80 mg per 250 ml, but a large specialty coffee can go over 500 mg. A bar or gel with a printed caffeine amount is easier to dose.
Our SUPR Bars come in three strengths, all from upcycled coffee fruit: 20 mg Blueberry Cashew, 40 mg Cocoa Almond and 60 mg Espresso Peanut Butter. Being real food, they're best eaten before the start or on easier stretches. In the last hour of a marathon, most runners prefer a gel.
What about carbs?
Caffeine isn't fuel. For a marathon you still need carbohydrate, and sports science guidance (Jeukendrup, 2014) suggests about 30–60 g per hour for efforts of 1–2.5 hours and up to 90 g per hour for longer efforts. Plan your caffeine around your carb plan, not instead of it.
Race-week checklist
- Work out your dose (body weight × 2–3).
- Test it on two long runs at goal pace.
- Count every source: coffee, gels, bars, cola at aid stations.
- Stay under 200 mg at once and 400 mg for the day.
- For an afternoon race, think about your sleep that night.
FAQs
Should I cut out caffeine before race day?
The AIS says withdrawing caffeine before competition to boost its effect isn't supported. Keep your normal routine.
Can caffeine upset my stomach?
It can. Side effects include a higher heart rate, jitters and gut discomfort, and some athletes don't respond well at all. That's why you test it in training first.
Is 60 mg enough to make a difference?
For a 60 kg runner, 60 mg is 1 mg/kg, below the 2 mg/kg minimum seen in the research. Most runners will want more than one 60 mg serve, or a 60 mg serve plus their usual coffee.
Sources
- Australian Institute of Sport – Caffeine supplement fact sheet
- Guest NS et al. (2021) ISSN position stand: caffeine and exercise performance
- Jeukendrup A (2014) A step towards personalized sports nutrition: carbohydrate intake during exercise
General information only, not individual advice. Talk to a sports dietitian about your own race plan, and check with your doctor if you're pregnant or have a heart condition.