Nighttime leg cramps are sudden, painful muscle contractions that usually affect the calves, feet, or thighs. They can wake you from sleep and leave the muscle sore for a while afterward.

In most cases, they are harmless. But if they happen frequently or come with swelling, weakness, numbness, or other unusual symptoms, it is worth paying attention.

1. Muscle Fatigue

One of the most common reasons for nighttime cramps is tired muscles.

They may appear after:

• Long walks
• Intense exercise
• Standing for many hours
• Suddenly increasing activity
• Repetitive leg movements

Overworked muscles can become more prone to involuntary contractions during sleep.

2. Dehydration

Not drinking enough fluid can sometimes contribute to cramps, especially after sweating heavily or spending time in hot weather.

Possible signs of dehydration include:

• Thirst
• Dry mouth
• Dark urine
• Dizziness
• Fatigue

However, dehydration is not the cause