Symptoms
Muscle cramps: why they happen and how to relieve them
Is this an emergency?
This is not an emergency service. Call 911 or go to the nearest emergency room if you have:
- Calf pain with a swollen, red or warm leg
- Severe muscle pain with dark (red or cola-colored) urine or passing little urine
- Cramps with confusion, very hot skin or fainting in the heat
- Severe muscle weakness that keeps you from walking
Help lines
Muscle cramps are muscle contractions that don’t let go on their own, most often in the calf or thigh. They usually come from overusing a muscle, dehydration or heat, and they ease with stretching and massage. If they keep coming back, the doctor reviews your medicines and, if needed, gives you a lab order for blood tests.
Other names: Leg cramps, Charley horse, Muscle spasm
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Possible causes
Exercise, heat and dehydration
Heavy sweating in the heat; better with fluids and electrolytes
Dehydration
Thirst, dry mouth and dark urine
Diuretics and low potassium
Water pills can lower potassium
Underactive thyroid
Tiredness, feeling cold and dry skin
Kidney problems
Checked with blood tests
Pregnancy or menstruation
Cramps are more frequent at those times
Blood clot in the leg
Pain that won’t go away with a swollen, warm leg: ER
On this page(8)
What are muscle cramps?
A cramp is when a muscle tightens without you trying to tighten it, and it doesn’t relax. The muscle feels hard or bulging and it hurts. According to MedlinePlus, the most common places are the back of the lower leg (the calf) and the back and front of the thigh; cramps also happen in the feet, hands, arms, belly and along the ribs.
They are very common and can usually be stopped by stretching the muscle.
Your doctor
Dr. Diana Nieves Castro, MD
General practice physician
Several years of emergency-department experience.
Founding Executive Director of The Health Initiative.
Causes of muscle cramps
According to MedlinePlus, cramps can come from:
- Overusing or injuring a muscle, for example during exercise
- Dehydration and low minerals such as sodium, potassium or calcium. In Puerto Rico’s heat, heavy sweating makes them more likely: see heat cramps and heat stroke and dehydration
- Medicines: diuretics (water pills) can lower potassium; cholesterol statins are among the medicines that rarely cause serious muscle damage
- An underactive thyroid: see hypothyroidism
- Kidney problems: see high creatinine
- Pregnancy and menstruation
- Heavy drinking
How to stop a cramp
MedlinePlus recommends:
- Stopping the activity and stretching the muscle: for the calf, straighten your leg and pull your toes toward you
- Massaging the muscle
- Using heat when the cramp starts, and ice once the pain has improved
- If the muscle is still sore, an over-the-counter anti-inflammatory may help
- Drinking water; if you sweated a lot, a sports drink helps replace minerals
Leg cramps at night
Many leg cramps strike at night and wake you with a hard, knotted calf. The causes are the same as above: a day of hard work or long hours on your feet, too little water, heavy sweating in the heat, or a medicine such as a diuretic.
When one hits, sit or stand, straighten your leg and pull your toes toward you until the muscle lets go, then massage it. To have fewer, drink enough water during the day and make calf stretches part of your routine. If cramps wake you several nights a week, an evaluation and a blood test are worth it.
How to prevent leg cramps
To have fewer cramps, MedlinePlus advises exercising within your ability, drinking plenty of fluids while you exercise, eating foods with potassium (such as orange juice and bananas) and stretching to improve flexibility.
How we help by video
You see Dr. Diana Nieves Castro, a Puerto Rico-licensed general practice physician with several years of emergency-department experience, in English or Spanish. She asks when the cramps started, how long they last, how often they happen, which muscles, whether you have had vomiting, diarrhea or heavy sweating, whether you are pregnant, which medicines you take and whether you exercise hard or drink alcohol.
We evaluate, diagnose and treat. If the cramps are severe or keep coming back, we give you a lab order for a lab near you: electrolytes (potassium, calcium, magnesium), kidney function, thyroid and glucose. We check whether any of your medicines could be causing them. If appropriate, the doctor prescribes and we send your prescription to your pharmacy.
Quinine is not for cramps: according to MedlinePlus, it should not be used to treat or prevent nighttime leg cramps, because it has not been shown to work and can cause serious side effects.
Doctor online 24/7: if cramps wake you at night, video visits are available around the clock on your phone or computer. An online doctor visit has the same price for every age.
When a cramp is an emergency
Go to the ER if you have:
- Calf pain that won’t go away, with a swollen, red or warm leg: it may be a blood clot, not a cramp. See swollen legs
- Severe muscle pain with dark urine (red or cola-colored) or passing little urine, especially after hard exercise, heat or a fall: it may be rhabdomyolysis, a muscle injury that damages the kidneys
- Cramps with confusion, very hot skin or fainting in the heat: it may be heat stroke, call 911
Frequently asked questions
Why do I get leg cramps at night?
What helps muscle cramps fast?
Why do I get foot cramps?
What vitamin or mineral am I missing if I get cramps?
When should I worry about muscle cramps?
Can cholesterol medicines cause cramps?
Related topics
About this page
Author: The Health Initiative
Medical care provided by Dr. Diana Nieves Castro, MD (PR license 24027)
Disclosure: Founding Executive Director of The Health Initiative
Published: 2026-10-02 · Updated: 2026-10-11
Sources (7)
- Muscle cramps (MedlinePlus, NIH) (opens in a new tab) (accessed 2026-10-02)
- Rhabdomyolysis (MedlinePlus, NIH) (opens in a new tab) (accessed 2026-10-02)
- Low blood potassium (MedlinePlus, NIH) (opens in a new tab) (accessed 2026-10-02)
- Quinine (MedlinePlus, NIH) (opens in a new tab) (accessed 2026-10-02)
- Deep vein thrombosis (MedlinePlus, NIH) (opens in a new tab) (accessed 2026-10-02)
- Heat emergencies (MedlinePlus, NIH) (opens in a new tab) (accessed 2026-10-02)
- Heat-related illnesses (CDC, NIOSH) (opens in a new tab) (accessed 2026-10-02)
