How much sodium do you need per hour when running in South African heat?

How much sodium do you need per hour running in South African heat?

There is no evidence-based hourly number that suits everyone. The ACSM fluid-replacement position stand suggests drinks containing about 0.5–0.7 g of sodium per litre in events lasting over an hour, so the hourly amount depends on how much you drink, how much you sweat and how salty your sweat is. For shorter runs, normal meals usually cover sodium.

Why does it vary so much?

Your loss per hour is sweat rate times sweat sodium concentration. Reviews report sweat sodium commonly spanning about 10–90 mmol/L between athletes (1 mmol of sodium is 23 mg, so about 230–2 070 mg per litre), and sweat rates of roughly 0.5–2 L an hour, sometimes over 3 L in heat.

These are our calculations from published ranges. You do not need to replace everything: the body has stores, and replacing a portion of losses with fluid you drink to thirst is the usual approach.

How do you find your own number?

1. Weigh yourself nude before and after a 60-minute run at race pace, noting what you drank.
2. Each 1 kg lost, plus fluid drunk, is roughly 1 L sweated.
3. White salt crusts on your kit, stinging eyes or a salty taste suggest salty sweat.
4. Repeat in hot conditions; Durban or Lowveld humidity can raise sweat rate significantly.

How do you get the sodium in practice?

Most sodium comes from food and drink. Product labels are inconsistent, as South African sachets rarely publish sodium per serving:

• Maurten Gel 100 has about 20 mg and Biogen Liquid Energy Gel about 29 mg per gel, so gels barely contribute.
• Rehidrat Oral has about 288 mg per 14 g sachet by our calculation (R108–R121 for 6, Dis-Chem and Clicks, October 2026), but it is indicated for diarrhoea, not racing.
• A quarter teaspoon of fine table salt is roughly 1.5 g of salt, or about 590 mg of sodium (sodium is 39% of salt by weight).
• REVIVE, Biogen Electrolyte and other sachets do not publish sodium on the retailer pages we reviewed.

See best electrolyte powder in South Africa and the electrolyte comparison.

What is the hyponatraemia risk?

Exercise-associated hyponatraemia (blood sodium below 135 mmol/L) is mainly caused by drinking more than you sweat, especially in events longer than four hours and for slower runners. Sodium in your drink slows it but cannot prevent it if you overdrink. The consensus advice is to drink to thirst. Symptoms include nausea, headache, confusion and seizures and need emergency care. See what is hyponatraemia in endurance events.

Who should be careful?

People with hypertension, heart or kidney disease, or on diuretics should not use high-sodium strategies without medical advice. Also see do salt tablets prevent cramps. This is general information, not personal medical advice.

Under-18s and pregnant runners should get individual advice rather than use salt or high-sodium products.

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