Hydration Planner: How Much to Drink in Singapore's Heat

It depends on how long and how hard you go, your body weight, how much you sweat and the heat stress on the day. As a general guide for healthy adults:

• Before: about 5–7 ml per kg of body weight, 2–4 hours before you start.
• During: small, regular sips, often around 400–800 ml an hour for sweaty sessions in Singapore's heat.
• After: about 1.25–1.5 times the fluid you lost, spread over the next few hours.

The Hydration Planner above works out your numbers using live heat stress where you are.

WBGT (Wet Bulb Globe Temperature) measures how hard the heat is on your body. It combines air temperature, humidity, sun and wind, so it's a better guide for exercise than temperature alone. Singapore's National Environment Agency (NEA) publishes live readings across the island in three bands: Low (below 31°C), Moderate (31 to below 33°C) and High (33°C and above). When it's High, consider shortening your session, easing off or training at a cooler time.

For short, easy sessions of under about 45 minutes, water is usually enough. For longer or harder sessions, or in hot and humid conditions, an isotonic drink with electrolytes and carbohydrates helps replace the sodium you lose in sweat and keeps your energy up.

Weigh yourself before and after a typical session, in minimal clothing and after towelling off. Every 1 kg lost is roughly 1 litre of sweat. Add the amount you drank during the session, then divide by the hours you trained to get your sweat rate per hour. Use the result to choose Light, Average or Salty / heavy in the planner.

100PLUS ACTIVE is made for active moments like running, football, basketball, badminton and tennis. 100PLUS PRO High Protein adds 10 g protein and 2 g BCAA for recovery after gym, fitness and hybrid racing. 100PLUS Zero Sugar suits everyday hydration, like concerts and days out. 100PLUS Effervescent Tablets and ACTIVE Isotonic Powder sachets pack light for travel and racing overseas.

Flights, new climates and different drinks on course make it easy to fall behind. Pack light options you can mix with any bottle of water, such as effervescent electrolyte tablets (follow the pack: 1 tablet in 200 ml, 1–2 a day) and isotonic powder sachets for your training runs and race day. Check the race's weather forecast and switch the planner to Overseas to plan for the climate.

Watch for thirst, a dry mouth, dark urine, headache, dizziness, muscle cramps, nausea and unusual tiredness. Stop, move to shade, cool down and drink. If someone becomes confused, stops sweating or collapses, treat it as an emergency and call 995.

Yes. Drinking far more than you sweat, especially plain water over long events like a marathon, can dilute the sodium in your blood (hyponatraemia), which can be dangerous. Aim to replace what you lose rather than drink as much as possible, and include electrolytes on long, sweaty days.