5 Signs You're Drinking Wrong (And the Calculator That Will Fix It)
Hydration is one of those topics where it's easy to mess up in both directions. Drink too little β you suffer. Drink too much β you suffer even more. Here's how to tell if something's off.
Fun fact: since 1981, there have been 14 recorded deaths from overhydration at endurance events. From dehydration β zero.
This doesn't mean dehydration is safe. It means we runners have managed to overdo the "drink more water" advice to literally deadly consequences.
Let's break down five signs that something's wrong with your hydration β in one direction or the other.
Sign 1: You Finish Heavier Than You Started
What it means: You're drinking too much.
This is not a joke or a typo. If after a workout or race you weigh the same or more than before β you've overdrunk. Literally.
Excess water doesn't just disappear. It dilutes your blood, lowers sodium concentration, and in severe cases causes hyponatremia β a condition that can lead to brain swelling and death.
How to fix it:
- Weigh yourself before and after workouts
- Normal loss: 1-3% of body weight
- If weight unchanged or increased β drink less next time
Red flags for hyponatremia:
- Swelling of hands and feet
- Nausea, vomiting
- Headache
- Confusion
- Seizures
If you feel these after a race β don't drink more water! Seek medical attention.
Sign 2: Your Urine Is Dark Yellow or Orange
What it means: You're drinking too little (or haven't drunk in too long).
Urine color is the simplest hydration indicator. Here's how it works:
| Color | Status |
|---|---|
| Clear | Overhydrated (yes, this is also bad) |
| Light yellow | Perfect |
| Yellow | Normal, could drink |
| Dark yellow | Dehydrated, need to drink |
| Orange/brown | Severely dehydrated, drink urgently |
How to fix it:
- Check color first thing in the morning
- If darker than "light yellow" β drink 300-500 ml within an hour
- Before training β aim for light yellow
Note: Some vitamins (especially B vitamins) turn urine bright yellow regardless of hydration. Keep this in mind.
Sign 3: Heart Rate "Drifts" in the Second Half of Training
What it means: Likely dehydration and cardiac drift.
Scenario: you start training, first 30-40 minutes everything's great. Pace 5:30/km, heart rate 145. Then same pace, but heart rate is now 160. Another 20 minutes β 170.
This is cardiac drift. Blood thickens from water loss, heart has to beat faster to pump the same volume.
How to fix it:
- On long workouts (60+ minutes) drink regularly
- 100-200 ml every 15-20 minutes
- If heart rate already drifted β try drinking, it'll ease up in 10-15 minutes
Important: Cardiac drift can also come from heat or fatigue. But if it appears specifically after 30-40 minutes without drinking β it's probably the water.
Sign 4: You Drink Strictly on Schedule, Ignoring Thirst
What it means: You're following outdated recommendations.
There was an era in sports science β roughly 1990s-2000s β when the advice was "drink before you feel thirsty" and "drink as much as possible." Some sources still repeat this.
Modern consensus is different: thirst is a reliable mechanism, honed by millions of years of evolution. A healthy body knows very well when it needs water.
When a schedule is justified:
- During races (adrenaline can suppress thirst)
- On ultra distances (accumulated deficit)
- In extreme heat
- When water isn't constantly available
When drinking by thirst is enough:
- Regular training
- Moderate weather
- Water at hand
How to fix it:
- Don't force yourself to drink if you don't want to
- But have water available to drink when you do
- In races β plan, but adjust based on feel
Sign 5: You Don't Know Your Sweat Rate
What it means: You're guessing instead of measuring.
Sweat rate is your key number in hydration. For some it's 0.6 L/hour, for others 2.0 L/hour. The difference is more than threefold.
Without this number, all recommendations like "drink 500-800 ml/hour" are shots in the dark. For one person it's too little, for another β too much.
How to find your sweat rate:
- Weigh yourself naked β Weight A
- Run 60 minutes in typical conditions
- Record how much you drank β Water
- Weigh yourself naked β Weight B
- Sweat Rate = (Weight A - Weight B) + Water
Example:
- Weight before: 68.0 kg
- Weight after: 67.2 kg
- Drank: 300 ml
- Sweat Rate = (68.0 - 67.2) + 0.3 = 1.1 L/hour
Now you know: to replace 70-80% of losses, you need ~0.8 L/hour in those conditions.
How to fix it (if you're too lazy to test):
Use the water loss calculator. It will estimate your approximate sweat rate based on weight, intensity, temperature, and humidity. Not as accurate as a real test, but much better than guessing.
Bonus: Sign 6 β You Only Drink Water on Long Workouts
What it means: You're forgetting about electrolytes.
For workouts shorter than 60-90 minutes, plain water is fine. For long ones (2+ hours) β not anymore.
Sweat carries away not just water, but sodium too. If you replace water but not sodium β you're diluting your blood and approaching that same hyponatremia.
How to fix it:
- On 2+ hour workouts: sports drink or electrolyte tablets
- Or salty food at aid stations (chips, salted nuts β yes, this works)
- Rough guideline: 300-700 mg sodium per liter of fluid
Summary: Quick Checklist
| What to check | Good | Bad |
|---|---|---|
| Weight after vs before | Minus 1-3% | Plus or unchanged |
| Urine color | Light yellow | Dark or clear |
| Heart rate during training | Stable | "Drifts" after 30-40 min |
| Drinking strategy | By thirst + race plan | Strictly by timer always |
| Sweat rate knowledge | Know my number | Don't know |
| Electrolytes on long sessions | Using them | Water only |
If you have more than two checks in the "Bad" column β time to rethink your approach.