Proper hydration and recovery practices are essential for getting the most from your infrared sauna sessions while minimising potential downsides. Sweating is central to the sauna experience, but losing significant fluid and electrolytes requires thoughtful replacement to maintain performance, comfort, and safety.
This guide covers evidence-based strategies for hydration before, during, and after sauna use, along with recovery practices that help your body adapt and thrive with regular heat therapy.
Understanding Sweat Loss
During a typical 30-45 minute infrared sauna session, you can expect to lose anywhere from 300ml to over 800ml of sweat. Several factors influence how much you sweat:
- Session duration: Longer sessions mean more sweat loss
- Temperature settings: Higher temperatures increase sweating
- Individual variation: Some people naturally sweat more than others
- Acclimatisation: Regular users often sweat more efficiently
- Hydration status: Well-hydrated bodies sweat more effectively
What's in Sweat?
Sweat is primarily water (about 99%), but it also contains:
- Sodium chloride (salt): The primary electrolyte lost through sweat
- Potassium: Important for muscle and nerve function
- Magnesium: Involved in hundreds of bodily processes
- Trace minerals: Zinc, copper, and others in small amounts
- Metabolic waste: Urea, lactate, and other compounds
The goal of sauna hydration isn't just replacing water—it's maintaining fluid balance while supporting electrolyte levels. Plain water works for occasional, moderate sessions, but frequent or long sessions may benefit from electrolyte supplementation.
Pre-Session Hydration
Daily Baseline
Good sauna hydration starts with good daily hydration. If you're chronically under-hydrated, no amount of pre-session drinking will compensate. Aim for 2-3 litres of water daily, more if you're active or live in hot climates.
The Hours Before
In the 2-3 hours before your session:
- Drink 500-750ml of water steadily (not all at once)
- Avoid caffeine if possible, as it's a mild diuretic
- Avoid alcohol, which impairs thermoregulation and dehydrates
- Consider adding electrolytes if you're a heavy sweater or planning a long session
Immediately Before
About 15-30 minutes before entering the sauna, drink another 250ml of water. Your urine should be light yellow at this point—dark urine indicates you need more fluids.
Pre-Session Protocol
- 2-3 hours before: 500-750ml water with optional electrolytes
- 15-30 minutes before: 250ml water
- Check: Urine should be light yellow
- Avoid: Caffeine and alcohol
During Your Session
Keep Water Nearby
Always have water within reach during your session. Don't wait until you're thirsty—by then, you're already somewhat dehydrated. Take small sips every 5-10 minutes.
How Much to Drink
Aim to drink 200-400ml during a 30-minute session. This won't fully replace sweat losses, but it helps maintain hydration levels and supports sweating.
Water Temperature
Room temperature or slightly cool water is ideal during sessions. Very cold water may cause stomach discomfort and isn't absorbed as quickly. Very warm water may feel uncomfortable when you're already hot.
Post-Session Recovery
Immediate Rehydration
After exiting the sauna, your fluid replacement priority should be:
- First 15 minutes: Drink 250-500ml of water while resting and cooling down
- First hour: Continue drinking, aiming for 500-750ml total
- Following hours: Continue hydrating until urine returns to light colour
Electrolyte Considerations
For occasional 20-30 minute sessions, plain water is usually sufficient. Consider electrolyte supplementation if you:
- Use the sauna daily or multiple times daily
- Have sessions exceeding 45 minutes
- Are a "heavy sweater"
- Exercise before your sauna session
- Experience muscle cramps or fatigue after sessions
Electrolyte Options
- Electrolyte tablets or powders: Convenient and precisely dosed
- Coconut water: Natural source of potassium and some sodium
- Homemade drinks: Water with a pinch of salt and splash of fruit juice
- Sports drinks: Effective but often high in sugar—look for low-sugar options
Drinking excessive water without electrolytes can lead to hyponatremia (low blood sodium), which is potentially serious. If you're drinking large volumes (over 1.5L in an hour), add electrolytes to avoid diluting your blood sodium too much.
Physical Recovery Practices
Cool-Down Period
After exiting the sauna:
- Rest for 10-15 minutes at room temperature before showering or being active
- Avoid sudden cold exposure like cold showers or jumping in cold pools (unless you're experienced with contrast therapy)
- Let your heart rate return to normal—this typically takes 5-10 minutes
Showering
Once cooled, take a lukewarm shower to wash away sweat and any impurities released through your skin. You can gradually make the water cooler if you enjoy contrast, but extremes aren't necessary for benefits.
Rest and Relaxation
The post-sauna window is an excellent time for:
- Meditation or quiet reflection
- Light stretching (muscles are warm and pliable)
- Rest and relaxation—don't rush back to stressful activities
- Napping (many people feel pleasantly drowsy after a session)
Nutrition for Sauna Users
Post-Session Eating
After your session and rehydration:
- Wait at least 30 minutes before eating a heavy meal
- Light snacks are fine if you're hungry
- Foods rich in potassium (bananas, avocados, sweet potatoes) support electrolyte balance
- Protein and healthy fats support recovery if you've combined sauna with exercise
Foods to Support Regular Sauna Use
For frequent sauna users, consider incorporating these into your diet:
- Leafy greens: Rich in magnesium and potassium
- Nuts and seeds: Good sources of minerals
- Fatty fish: Omega-3s may support cardiovascular health
- Fruits: Natural electrolytes and hydration
Signs You Need to Adjust Your Approach
Dehydration Indicators
- Dark urine for several hours after your session
- Headache during or after sessions
- Dizziness or lightheadedness
- Excessive thirst
- Dry mouth or lips
Electrolyte Imbalance Signs
- Muscle cramps, especially in legs
- Fatigue that seems disproportionate
- Irregular heartbeat or palpitations
- Weakness or lack of energy
For the first few weeks of regular sauna use, pay attention to how you feel after sessions. Adjust your hydration strategy based on what you notice. Everyone's needs are slightly different.
Special Considerations
Athletes
If you use the sauna for exercise recovery, be especially attentive to hydration. You may already be in a fluid deficit from training. Consider sauna sessions on lighter training days, and increase electrolyte intake accordingly.
Older Adults
Thirst sensation often decreases with age, making it easier to become dehydrated without realising it. Older adults should be proactive about drinking on a schedule rather than waiting for thirst.
Hot Weather
During Australian summers, you're already losing fluids to heat throughout the day. Increase baseline hydration on hot days, and consider shorter or less frequent sauna sessions during heat waves.
Creating Your Routine
The best hydration and recovery strategy is one that becomes habitual. Consider creating a simple routine:
- Begin drinking water 2-3 hours before your regular sauna time
- Prepare your water bottle before entering the sauna
- Follow a consistent cool-down routine
- Keep electrolyte supplements handy for longer sessions
- Monitor your urine colour as a hydration indicator
With consistent attention to hydration and recovery, infrared sauna sessions become a sustainable, beneficial part of your wellness routine. For more guidance, see our safety tips and first session guide.