What to Drink During a Marathon

Written by the Hammer Nutrition UK editorial team. Content reviewed for accuracy against published sports-science consensus statements. Published: August 2026. Last updated: August 2026.

How we developed this guidance: This article draws on the ACSM Exercise and Fluid Replacement position stand, the International Exercise-Associated Hyponatraemia Consensus Statement, and the World Athletics Nutrition for Athletics Consensus Statement. Product references reflect Hammer Nutrition UK's formulations; individual responses vary and this guidance does not replace advice from a qualified sports dietitian or medical professional.

A practical marathon hydration plan is not "drink as much as possible" or "take water at every station". Start normally hydrated, use your measured sweat rate to set a sensible upper limit, and drink according to thirst within a plan you have rehearsed in training. Depending on the conditions and your fuelling strategy, that may mean water plus electrolytes, or a carbohydrate-electrolyte drink such as HEED — Hammer's recommended option for runners who want fluid and carbohydrate together. Too little fluid can impair comfort and performance; too much can lead to exercise-associated hyponatraemia. The winning approach sits between those extremes.

Choose by expected race duration: HEED combines carbohydrate energy and electrolytes for marathon efforts up to 3 hours. For events lasting longer than 3 hours, athletes who prefer sustained liquid fuel can consider Perpetuem as part of a strategy rehearsed in training. Compare our long-distance sports and energy drinks →

Safety note: A runner should never finish a race heavier than they started because of fluid intake. Headache, vomiting, confusion, altered behaviour, severe weakness or seizures during or after a marathon require urgent medical assessment. Do not assume the answer is more water or more electrolyte capsules.

Why marathon hydration is different from training runs

A marathon turns small mistakes into large ones. You are running longer and harder than on an easy run, often in warmer conditions or among crowds. Race-day nerves can also push the early pace.

Aid stations create fixed drinking opportunities. Crowded tables can make it tempting to grab a cup simply because it is there; over 26.2 miles, "just in case" drinking adds up.

Sweat and electrolyte losses accumulate, while gastrointestinal distress is more common at race pace. Test drink, fuel and electrolytes together — not as three plans assembled on race morning.

Shop our Running Sports drinks

The table below is a broad screening guide only. Published estimates vary with pace, body size, clothing, acclimatisation, humidity and individual physiology. Your own repeated tests are more useful than the row that appears to fit you.

Body weight	Cool (under 15°C)	Mild (15–20°C)	Warm (20–25°C)	Hot (25°C+)
Under 60 kg	400–600 ml/hr	500–700 ml/hr	700–900 ml/hr	900–1,100 ml/hr
60–75 kg	500–700 ml/hr	600–800 ml/hr	800–1,000 ml/hr	1,000–1,200 ml/hr
Over 75 kg	600–800 ml/hr	700–900 ml/hr	900–1,100 ml/hr	1,100–1,400 ml/hr

These are possible sweat rates, not automatic drinking targets. Many marathon runners drink roughly 400–800 ml per hour, then adjust from training evidence, thirst, pace and weather. If your test suggests a very high requirement, seek individual advice from a qualified sports dietitian rather than forcing more than your stomach can comfortably absorb.

Sodium loss: why water alone may not be enough

Sweat sodium concentration is highly individual. A salty crust on dark kit may suggest you are a "salty sweater", but laboratory or patch testing is more precise.

Water remains useful, especially with concentrated fuel. The problem is excessive intake of any low-sodium fluid — including some sports drinks — relative to what you are losing. Electrolyte products do not make unlimited drinking safe, and hyponatraemia cannot reliably be prevented by taking capsules while continuing to overdrink.

Hammer takes a full-spectrum approach rather than trying to replace every milligram of sodium lost. Endurolytes capsules separate electrolytes from calories; Endurolytes Fizz adds electrolytes to a bottle; and Endurolytes Extreme provides a higher-strength option for hotter conditions or heavier sweaters. Individual responses vary — start at the label dose and adjust from training experience.

Measured sweat rate	Example sodium loss at 750 mg/L	Practical starting point to test
Low: under 600 ml/hr	Under 450 mg/hr	Water or HEED plus 1–2 Endurolytes capsules/hr if needed
Moderate: 600–900 ml/hr	450–675 mg/hr	HEED or water plus 2–3 Endurolytes capsules/hr; alternatively test Fizz
High: over 900 ml/hr	Over 675 mg/hr	Test Endurolytes Extreme at its label dose; consider professional sweat testing

This is a testing framework, not a sodium-matching equation. Start conservatively, follow the label and adjust only from long-run experience. More sodium is not automatically better, and overly concentrated drinks or supplements can aggravate nausea in some runners.

Aid-station strategy: mile by mile

This example suits a roughly 4:00–4:30 runner in mild conditions where stations are spaced about two to three miles apart. Check your race map and convert the plan into actual station numbers before race day.

Miles 1–6: settle before you sip

Do not drink simply because the first table appears. If conditions are mild and you started normally hydrated, one or two small drinks of roughly 100–150 ml during this section may be enough. Use thirst and your rehearsed schedule. Take your first tested electrolyte dose around 30–45 minutes rather than tying it rigidly to mile three.

Miles 7–13: establish the rhythm

Use alternate stations if that matches your sweat-rate plan, taking roughly 100–200 ml at a time. Choose water when taking a gel; choose HEED when you want fluid and carbohydrate together. If carrying HEED, sip between stations and use course water as needed. Keep electrolyte timing based on elapsed time — usually every 45–60 minutes in the plan you tested — not mile markers alone.

Miles 14–20: stay with the plan

This is where an ambitious first half begins collecting interest. Do not suddenly double fluids, calories or capsules because the race feels harder. Continue your tested drink and electrolyte schedule. HEED can contribute carbohydrate, but for a marathon lasting beyond about two hours it should be part of a broader fuelling plan. Depending on what you tolerate, that may include Hammer Gel, Perpetuem or a tested solid fuel such as Perpetuem Solids or Hammer Bars.

Miles 21–26.2: no improvising

Continue small drinks according to thirst and the conditions. Take only fuel and electrolytes already scheduled and practised. The final miles are not the time to stack caffeinated products, chase a cramp with repeated capsules or force down several cups at once. If you feel confused, develop a severe headache, begin vomiting or cannot run normally, stop and seek the race medical team.

Finish line: begin recovery

Stop drinking to a race-hour schedule once you finish. Drink according to thirst and begin recovery. If it is part of your tested routine, mix two scoops of Recoverite in water and take it promptly after exercise, then follow with a normal meal. Recoverite is Hammer's recommended post-endurance recovery drink; individual tolerance varies.

What to drink in cool versus warm marathon conditions

Temperature changes the plan, but humidity, sun exposure, wind, pace and acclimatisation matter too. Use the ranges below as starting points for training — not compulsory quotas.

Conditions	Primary drink	Electrolyte option	Starting fluid range
Cool (under 15°C)	Water; HEED when carbohydrate is planned	Endurolytes capsules	400–600 ml/hr
Mild (15–20°C)	Water plus HEED	Endurolytes or Fizz	500–700 ml/hr
Warm (20–25°C)	HEED plus water as needed	Fizz or tested Extreme dose	600–800 ml/hr
Hot (25°C+)	HEED plus water, kept at tested concentration	Tested Extreme dose	Individualise; often 600–900 ml/hr

Do not automatically chase heat with litre after litre of plain water. Increase fluid only in line with measured sweat rate, thirst and tolerance. A pre-race electrolyte dose can be useful if it is consistent with the product label and has been tested in comparable training, but it is not insurance against heat illness. Adjusting pace may be the most important change on a hot day.

Carrying your own hydration versus using aid stations

Carrying a bottle gives you control over concentration and timing and helps you avoid congested stations. The trade-off is extra weight and the need to refill. A handheld bottle, belt or vest can work if the event permits it.

A practical setup is a 500 ml bottle of HEED plus dry Endurolytes capsules in a waterproof pouch. Use stations for water top-ups or gels. If relying on course drinks, confirm the brand, concentration and spacing, then test that setup in training.

What not to drink during a marathon

• Large volumes of plain water or sports drink "just in case". No drink prevents hyponatraemia if total fluid intake exceeds losses.
• Over-concentrated carbohydrate drinks, especially when also taking gels without water.
• Several caffeinated gels and drinks without tracking the total caffeine. Moderate caffeine does not automatically dehydrate you, but excess can worsen jitters, nausea and pacing errors.
• Anything you have not tested on long runs at marathon effort.

• Before the start: Normal breakfast and hydration; approximately 400 ml fluid in the final hour, plus the athlete's tested pre-race Endurolytes dose.
• Miles 1–13: Small drinks at alternate stations, one 500 ml HEED bottle carried, and Endurolytes on the rehearsed 45–60-minute schedule.
• Miles 14–26.2: HEED and water according to the planned hourly range, continuing electrolytes on time. Carbohydrate comes from the runner's full tested fuelling schedule — not one emergency gel at mile 18.
• Finish: Two scoops of Recoverite in water promptly after finishing, followed by a normal meal.

Frequently asked questions

Should I drink at every aid station?

Usually not. Use aid stations to execute a time- and volume-based plan, while responding to thirst and conditions. In the first half, avoid drinking through habit alone. Never drink so much that your body weight increases during the race.

What if I feel sick mid-race?

Slow down, stop forcing calories and fluid, and assess the situation. A few small sips of water may help if you have taken concentrated fuel, but nausea has many possible causes — including pacing, heat illness, overdrinking and gastrointestinal overload. Confusion, repeated vomiting, a severe headache or worsening symptoms require immediate medical help.

Is HEED suitable for marathon running?

Yes, as one part of a tested plan. HEED supplies carbohydrate and electrolytes and is formulated without citric acid, which some runners find easier to tolerate for digestive comfort. For a marathon lasting more than about two hours, pair it with an appropriate longer-duration fuelling strategy rather than expecting one bottle to supply all calories and electrolytes.

How do I know if I am hyponatraemic?

You cannot confirm hyponatraemia from symptoms alone because it can resemble dehydration or heat illness. Bloating, swollen hands, nausea and headache can occur, while confusion, altered behaviour, seizures or loss of consciousness are red flags. Stop drinking and seek urgent race-medical assessment; do not try to diagnose or treat it yourself with electrolyte capsules.

Build the plan, then rehearse it

Good marathon hydration is deliberately boring: familiar drink, familiar concentration, familiar timing. Measure your sweat rate, check the forecast and station map, then practise the complete plan at race pace. Confidence comes from evidence gathered in training — not a last-minute calculation in the start pen.

Shop our Running Sports drinks

Training for your first marathon? See our complete running nutrition range →

Sources and further reading

• American College of Sports Medicine — Exercise and Fluid Replacement position stand
• Hew-Butler T et al. (2015) — International Exercise-Associated Hyponatraemia Consensus Statement, British Journal of Sports Medicine
• World Athletics — Nutrition for Athletics Consensus Statement (2019)
• Minetto MA et al. (2021) — Evidence-based review of exercise-associated muscle cramps, PubMed / NCBI