Signs of Dehydration While Playing Tennis (and What to Do)
You're two games into the second set and your legs feel heavy. Your head is starting to ache. You can't tell if it's the opponent, the heat, or the fact that you've barely had a sip since warm-up.
Tennis makes it easy to miss the early signs of dehydration. Points are short, changeovers are quick, and you're concentrating on the match. This guide covers the common signs, what to do on court, and when to stop playing and get help.
Why Tennis Players Get Dehydrated
Sweat is how your body keeps cool, and tennis can produce a lot of it. USTA sports science reports that adults commonly lose around 1.0 to 2.5 liters of fluid per hour of singles in warm to hot conditions, and more in very hot ones. Many players finish a match having lost 2% or more of their body weight in fluid. The USTA article links even modest deficits to lower strength, endurance and mental performance.
Your sweat rate depends on heat, humidity, how hard you play and your own body, so two players on the same court can have very different needs.
Quick tip: Don't wait for thirst alone — it can lag behind what your body has already lost.
Common Signs of Dehydration During a Match
Early or mild dehydration can feel like ordinary match fatigue. MedlinePlus lists these among the signs of mild to moderate dehydration in adults:
- Thirst, though it can lag behind what your body has lost
- A dry or sticky mouth
- Darker yellow urine, or less of it
- Headache
- Muscle cramps
On a tennis court, you might also notice:
- Heavy legs or sudden tiredness that doesn't match how long you've been playing
- Slower reactions or trouble concentrating
- Feeling hotter than usual or struggling to cool down
These signs aren't specific to dehydration. Heat, a lack of sleep, not eating enough and fitness level can cause similar feelings. Our guide to why you feel so tired after tennis walks through the other common causes.
About Muscle Cramps
Muscle cramps can occur during tennis, but they are not a reliable sign of dehydration on their own. USTA sports science links heat-related muscle cramps to sodium loss and fluid loss. Cramps can have several causes, though, so don't assume a cramp always means you're dehydrated. If cramps are frequent or severe, talk to a doctor.
Stop and get help
Confusion, loss of consciousness, seizures, or suspected heatstroke are emergencies — call emergency services immediately. Do not wait for a temperature reading.
Signs That Mean Stop and Get Help
Some signs are more serious. MedlinePlus lists these among the signs of severe dehydration:
- Little or no urine, or very dark urine
- Dizziness or lightheadedness
- Confusion or unusual irritability
- Rapid heartbeat or rapid breathing
- Sunken eyes and listlessness
Stop playing and get out of the heat if you notice these. Call emergency services immediately for confusion, loss of consciousness, seizures, or suspected heatstroke. Do not wait for a temperature reading. Also get help if symptoms don't improve or get worse. These are not things to push through to finish the set.
What to Do If You Think You're Dehydrated
If your symptoms are mild:
- Pause the match and move to shade or a cooler spot.
- Sip fluids steadily rather than gulping a large amount at once.
- Add electrolytes if you've sweated heavily or played for a long time. USTA suggests a carbohydrate-electrolyte drink rather than plain water for matches longer than about an hour.
- Rest before deciding whether to keep playing. If you don't feel better, call it a day.
Our guide to what to drink after a tennis match covers rehydrating once you're off the court.
How to Stay Ahead of It
You don't have to wait for symptoms. A few habits help:
- Start well hydrated. USTA suggests drinking steadily in the days before a match and having 12 to 16 ounces about 60 to 90 minutes before play.
- Use changeovers as a reminder to check your hydration plan. Fluid needs vary with your sweat rate, conditions, and length of play.
- Know your sweat rate. Comparing your weight before and after a match can help estimate fluid loss, accounting for fluids consumed and urine passed. Our guide to staying hydrated before, during and after a match explains how.
- Replace electrolytes when it makes sense. Not every player needs them every time. Our guide to whether every tennis player needs an electrolyte drink can help you decide. If you'd like an electrolyte option for your tennis bag, AceFit Hydrate is a powdered electrolyte dietary supplement created for women in tennis — available in pouches of stick packs.
The Bottom Line
Heavy legs, a headache and darker urine can all be early signs that you're behind on fluids, but they aren't proof. Drink on a plan, know when to stop, and seek help promptly for serious symptoms.
Taking care of yourself is part of the game.
Frequently Asked Questions
What are the first signs of dehydration when playing tennis?
Often thirst, a dry mouth, a headache, heavy legs, and darker urine. Thirst can lag behind fluid loss, so don't rely on it alone.
Can dehydration cause muscle cramps in tennis?
It can contribute, particularly when you've lost a lot of sweat and sodium. USTA sports science links heat-related cramps to sodium and fluid loss. Cramps have other causes too, so see a doctor if they're frequent or severe.
How do I know if I'm drinking enough during a match?
Aim to drink at changeovers on a plan rather than waiting for thirst. After the match, urine that is very dark or scant suggests you need more fluid.
When should I stop playing because of dehydration or heat?
Stop playing if you feel dizzy, confused, faint, or very unwell, or if you experience a rapid heartbeat or rapid breathing. Seek emergency care for loss of consciousness, confusion, seizures or signs of heatstroke.
Does everyone dehydrate at the same rate?
No. Heat, humidity, intensity, fitness and individual sweat rate all affect how much fluid you lose.
This article is for general educational purposes only and isn't personal medical advice. If you have a health condition, take medication, or feel unwell, talk to a healthcare professional. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.