Urine color can provide a useful clue.
When you are well hydrated, urine is usually pale yellow. When your body needs to conserve water, the kidneys produce a smaller amount of more concentrated urine.
You may notice:
Dark yellow urine
Stronger-smelling urine
Urinating less often
These are recognized signs of dehydration.
However, certain foods, supplements, and medications can also change urine color.
3. You May Feel Tired or Weak
Dehydration can make ordinary activities feel harder.
Even relatively modest fluid loss may leave you feeling:
Tired
Weak
Sluggish
Less mentally alert
Fatigue is one of the common symptoms listed by both MedlinePlus and Mayo Clinic.
Fatigue alone has many possible causes, but if it occurs with thirst, dark urine, and reduced urination, dehydration becomes more likely.
4. Headaches Can Appear
