Caffeine for running – The best strategies, from 5K races to ultras
- Maryke Louw
- 3 days ago
- 9 min read
One of running’s worst-kept secrets is that caffeine boosts your performance. What is less well-known is how much caffeine to take, when, and in what form. Here’s our guide on how to get the most out of this wonderful substance for races over various distances.
Remember, if you need help with an injury, you're welcome to consult one of our physios online via video call.
This article contains affiliate links. We might earn a small commission on sales at no extra cost to you.
In this article:
This is how caffeine improves your running
The question with caffeine is not whether it improves running performance, but by how much – unlike with some other, more controversial supplements that might or might not improve your performance.
The International Olympic Committee and the International Society of Sports Nutrition agree that caffeine (taken within a certain dosage range - see below) enables runners to run faster at shorter distances and to run for longer before fatigue sets in in longer races.
How does it work?
Caffeine’s main effect is on the central nervous system. It blocks the receptors of adenosine, a chemical that causes drowsiness and fatigue, making your brain think that you’re less tired than you actually are. On a physiological level, it increases the release of calcium ions, which helps your muscles to produce more force and also delays fatigue later in a race.
Dozens of studies have shown that caffeine improves endurance performance on average by 2% to 4%. For context – this might shave up to 10 minutes off the time of a 4-hour marathoner. Note that these are average results – the effects of caffeine will vary between individuals due to factors such as genetics and training status.
While caffeine is useful for increasing performance in races as short as 5 km, its beneficial effects increase with longer events. This is mostly because mental alertness becomes more important the further you run. A study on sleep-deprived athletes found that strategically using caffeine to counteract drowsiness gave them about a 14% improvement in endurance.
What about side effects?
Side effects of caffeine include:
increased heart rate
headache (for people not used to caffeine, but also for habitual caffeine users who haven’t had their “fix”)
insomnia
anxiety
dehydration
“gastro-intestinal distress” (i.e. you’d better factor in a visit the Portaloo before the race).
However, these side-effects are mostly dose-dependent, so if you stick to the correct dosage (see below), you should be all right.
💡 Caffeine might have serious side effects if you have a heart condition or are prone to arrhythmia – it’s better to stay away from it if that’s the case.
How much caffeine to take and how – General guidelines
How much
The people in the white lab coats agree that between 3 mg and 6 mg of caffeine per kilogram of body weight per day is the “sweet spot”. Much less than that, and you don’t get an effect. Much more than that, and you don’t see any further increase in performance, but you run the risk of unwanted side effects kicking in.
So, for a runner weighing in at 70 kg (154 lbs) this means between 210 mg and 420 mg of caffeine per day. In practical terms, this would be anything from two to four cups of regular coffee at 240 ml (8 oz) per cup.
💡 Take care not to confuse milligrams and grams – it might lead to an overdose.
I would advise people who are not used to caffeine and/or doing shorter races to start off at the lower end of this range. Runners who are used to caffeine and/or doing longer races can likely take the higher suggested dose.
Keep track of your overall caffeine intake from all sources. For example, if you had a coffee at breakfast (100 mg) and an energy gel before the race (50 mg), and then you sip an energy drink during the race (say 100 mg), those add up. And note the US Federal Drug Administration’s guideline of a maximum of 400 mg of caffeine per day for adults.
The effects of caffeine can start within a wide time window, depending on how you take it. If you swallow the caffeine in some or other form (e.g. coffee or an energy drink), it is mostly absorbed in the stomach and small intestine and might take up to an hour to take effect. If you chew it (e.g. gummies or chewing gum), it already starts to get absorbed in your mouth, via your saliva, and its effects can take as little as 10 minutes to kick in.
The running benefits of caffeine can last from 2 to 4 hours after they have taken effect, after which it starts to taper off.
When your caffeine boost starts and ends is obviously important when timing your intake (either before and/or during a race) so that you reach peak performance when you most need it, so let’s look at the various ways to take it before we move on to race-distance specific advice.
How to take caffeine for running
Coffee
The way most of us take our caffeine when it’s not race day.
👍 Pros: It’s cheap and widely available, and it can be a calming and familiar morning ritual before a race.
👎 Cons: Coffee’s acidity and volume can sometimes cause stomach upset or acid reflux, especially if you have it black and/or on an empty stomach. The caffeine content in coffee can vary depending on the brew strength, beans, etc. – if you need a precise dose, you might prefer other methods.
Tea
Most types of tea have less caffeine than coffee – standard black tea has about 40–50 mg of caffeine per cup.
👍 Pros: A good option if you want a gentler caffeine boost. It’s less likely to cause jitters compared to coffee or energy drinks.
👎 Cons: You have to drink quite a lot of it to reach an effective dose for running performance.
Energy drinks
Depending on the brand, it will be sweetened with either sugar or artificial sweetener – check this if you want to be on top of your total energy intake before and during the race.
👍 Pros: Easy to find. The caffeine content is usually listed on the container, so you know the dosage.
👎 Cons: A high sugar content might cause a blood sugar spike-and-crash or stomach issues during a run, and the carbonation in many energy drinks can lead to burping or bloating while running. Bulky to carry during a race.
Gummies and chewing gum
Candy-like caffeinated gummies or caffeinated chewing gum.
👍 Pros: They are available in smaller doses of caffeine per unit, ranging from 25 mg to 125 mg, so you can spread out your caffeine intake strategically during longer races (see below). The caffeine kicks in fairly quickly because you chew them. Easier to carry with you than energy drinks or gels. No liquids involved.
👎 Cons: Chewing something while running hard isn’t for everyone. With chewing gum, you might not be able to extract the full dosage.
Here is a range of dosage examples available on Amazon – click through to see more flavours if these make your mouth pucker.
Caffeinated energy gels
A typical caffeine-infused energy gel packet contains about 20 mg to 50 mg of caffeine.
👍 Pros: Easy to carry. You can ingest caffeine alongside carbohydrates for energy in one go. Precise and small dosing if necessary.
👎 Cons: Doesn’t kick in as quickly as gummies or chewing gum. Some runners find that gels (with their thick, sugary consistency) can cause nausea, so practice in training. Some runners need liquids with which to wash down the gel.
Again, here's a range of dosages. If you click through, not all the flavour choices are necessarily caffeinated, so check for that.
Tablets
These are available over the counter (typically 100 mg or 200 mg of caffeine per tablet).
👍 Pros: Precise dosing – caffeine in pill form has been used in many research studies because it’s easy to standardise.
👎 Cons: Doesn’t kick in as quickly as gummies or chewing gum. Be very careful with pure caffeine powders or multiple pills, as it’s easy to overshoot the dose. Avoid sketchy “stimulant” combo products – some might also contain banned substances.
So, let’s take a look at how best to put these options to work in races over various distances.
5K race
When to take caffeine: 30–45 minutes before the race
How much to take: 2–3 mg/kg (140–210 mg for a 70 kg runner)
Best delivery methods:
Caffeinated chews/gummies (fast acting)
Caffeine chewing gum (fast acting)
Caffeine tablets (precise dosing)
Why this works: In a short, high-intensity race like a 5K, you want the caffeine to peak right at race time. Gum and dissolvable chews are perfect: they’re absorbed quickly through the mouth and cause less digestive distress than coffee. For experienced users who want precision, a tablet can work well too.
10K race
When to take caffeine: 30–45 minutes before the race
How much to take: 3–4 mg/kg (210–280 mg for a 70 kg runner)
Best delivery methods:
Caffeinated chews/gummies
Caffeine tablets
Coffee (if tolerated)
Why this works: A 10K requires sustained effort, and you want caffeine to kick in during the middle and late stages. Fast-absorbing methods like chews give a clean pre-race boost without excess fluid. Chews also combine fast absorption with slightly slower release, helping carry you through the full 40–60 minutes.
Half marathon
When to take caffeine:
Main dose: 45–60 minutes pre-race
Optional booster: 60 minutes into race
How much to take:
Pre-race: 3–4 mg/kg (210–280 mg for a 70 kg runner)
Mid-race: 50–100 mg
Best delivery methods:
Pre-race: Tablet or coffee
Mid-race: Caffeinated gel, chew, or gum
Why this works: You’ll be running for 1.5–2+ hours. The initial dose helps you settle into race pace with energy, while the booster prevents late-race fade. Chews and gum are compact, fast acting, and easy on the stomach, making them ideal during a hard run.
Marathon
When to take caffeine:
Main dose: 45–60 min before start
Boosters: Every 90–120 min
How much to take:
Pre-race: 3–4 mg/kg (210–280 mg for a 70 kg runner)
During: 50–100 mg each booster
Total limit: 400 mg/day
Best delivery methods:
Pre-race: Tablet or coffee
During: Caffeinated gels, chews, or gum
Why this works: Marathons demand stamina and mental endurance. Use a solid pre-load plus mid-race caffeine to stay focused, especially around the "wall" (~30 km). Chews and gum kick in quickly and are easy to carry, while gels combine caffeine and carbs.
Single-day ultramarathon (50–100K)
When to take caffeine:
Skip at race start unless you're groggy
Begin small, regular doses around hour 2–3
Continue every 1–2 hours as needed
How much to take:
Per dose: 50–100 mg
Total daily max: 400 mg
Best delivery methods:
Early/mid-race: Caffeinated chews or gels
Late in race: Chew or gum for fast relief, or tablet if major fatigue
Why this works: In ultras, it's smarter to delay caffeine until fatigue or low energy sets in. Frequent small doses help maintain focus and stave off crashes. Chews and gum let you fine-tune the timing, while tablets are best saved for when you need a powerful wake-up.
Multi-day ultramarathon
When to take caffeine:
Avoid caffeine during Day 1 / early stages
Use sparingly in late hours or overnight
Prioritize caffeine during critical decision periods or sleep-deprived moments
How much to take:
50–100 mg doses
Stay under 400 mg per day
Best delivery methods:
Morning: Coffee or tablet
During: Chews, gum
Emergency alertness: Strong chew or strong gum
Why this works: Over days, sleep and recovery matter more than quick boosts. You’re not looking for constant stimulation. Instead, treat caffeine like a tool: use chews or gum to stay alert during night sections or when sleep deprived. Save tablets for intense fatigue or final efforts.
Finally, there was an interesting study done on multi-day cross-country skiers that showed that caffeine taken over more than one day in endurance events leads to more muscle damage (due to the increased effort it enables) but still increases overall performance.
About the Author
Maryke Louw is a chartered physiotherapist with more than 20 years' experience and a Master’s Degree in Sports Injury Management. Follow her on LinkedIn and ResearchGate.
