Heat cramps are painful muscle spasms caused by dehydration and electrolyte loss. They can be brought about by strenuous activity, hot weather, and other causes.

Heat cramps are the initial symptom of heat illnesses including heatstroke, a potentially deadly reaction to the body overheating.

You don’t have to be an athlete to get heat cramps. At-risk populations include older adults, infants, and children. City dwellers and people without access to adequate shelter or water are also at risk.

But you can treat heat cramps and avoid heat illness. Read on to learn about the symptoms, treatment, and prevention of heat cramps.

Heat cramps can be caused by illness, activity, and heat. Specific causes include:

Dehydration and electrolyte loss

Heat cramps are caused by severe fluid and electrolyte loss, especially sodium.

Dehydration is defined as the significant loss of bodily fluids. Fluid is a component of blood, and it’s needed to transport nutrients throughout the body. Bodily fluid also helps to control body temperature.

Dehydration can be caused by:

  • not drinking enough fluid
  • sweating excessively
  • engaging in intense activity, especially in the heat
  • running a high fever
  • having diarrhea
  • vomiting

It’s especially important to watch for dehydration symptoms in infants, babies, and small children. The following table lists symptoms of dehydration in adults and children.

Symptoms of dehydration in adultsSymptoms of dehydration in infants, babies, and children
thirstno wet diaper for 3 hours
dry mouth and tongueno tears while crying
headachesunken soft spot on the top of the head (fontanelle)
dark urinesunken eyes and cheeks

During exercise and outdoor jobs

Whether it’s through exercise or labor, physical exertion can cause excessive sweating and fluid loss. Strenuous activity and copious sweating can lead to dehydration, electrolyte reduction, and heat cramps. This may be more likely to occur in hot temperatures, although it can also happen when it’s cold.

If you’re working or exercising outside during cold weather, you’re probably wearing layered clothing. Clothing can reduce the ability of sweat to evaporate and cool down skin. This can cause overheating, no matter what the temperature outside.

Being outside may also limit your access to water or other fluids, making it hard to rehydrate quickly and efficiently.

High humidity and temperatures

You don’t need to be out in the noonday sun to experience the ill effects of hot weather and high humidity.

Heat causes your internal temperature to rise. Your body attempts to cool itself down by sweating profusely and radiating heat out through the skin. If you don’t ingest more fluids and electrolytes than you’re losing, this natural cooling system will stop working efficiently.

You can become severely overheated and dehydrated outdoors or inside. The body’s internal temperature can rise to dangerous levels, even if you’re doing nothing more than sitting quietly in a very hot room with poor air circulation.

Age is a factor

Children and adults over 60 are more susceptible to dehydration, heat cramps, and heat illness than people in other age groups. These conditions can also be more severe or dangerous when they occur in these populations.

In young people

Babies, children, and adolescents don’t adjust as quickly as adults to temperature changes and environmental heat. This makes them more vulnerable to heat cramps and heat stroke.

Children also sweat less and produce more body heat than adults do. If your child refuses to put on a coat when they’re outside, and you’re freezing despite wearing many layers, this is why. Their body is simply warmer than yours.

In older people

As people age, their bodies become less efficient at temperature regulation. This may be caused, at least in part, by the shrinkage of sweat glands. Sweat glands become diminished in size as part of the natural aging process. Less sweat equals less perspiration and a diminished ability to cool the body down.

Heat cramps can come on slowly or quickly. They often start out as involuntary muscle twitches that you may not notice until they progress.

What they feel like

Symptoms of heat cramps include:

  • muscle spasms, which can be debilitating
  • involuntary jerking movements
  • muscle pain, which can be severe
  • profuse sweating
  • moist, flushed skin
  • running a fever

Location

Heat cramps occur in voluntary muscles (muscles you can move on your own). Common locations are:

  • legs
  • arms
  • back
  • abdomen

How long do they last?

Heat cramps are usually brief, but they can be longer lasting. They may also come and go intermittently.

Heat cramps may stop without intervention, although taking immediate action can lessen their severity. It can also stop them from escalating to a more serious condition.

To relieve heat cramps, try these strategies:

Rest

  • Stop engaging in physical activity, and move to a cool location with good air circulation.
  • Keep your body in a prone, resting position.
  • If you’re wearing heavy clothing, remove layers.
  • Cool down your body by placing a cool compress on your face, neck, or chest.
  • Don’t resume strenuous activity.

Hydrate

  • Replacing fluids is essential.
  • The best things to drink are cool water, clear juices, or beverages that contain electrolytes, such as sports drinks or Pedialyte.
  • Look for beverages that list sodium and potassium as ingredients on the label.
  • Continue to hydrate after the heat cramps have stopped.

Stretching and massage

Massage and stretch out cramped muscles slowly and gently.

Range of motion exercises that gently stretch out the affected muscles can be beneficial. Make sure to go slowly.

Strategies to prevent heat cramps include the following:

  • Remain hydrated at all times by drinking lots of water or other fluids.
  • Drink lots of fluid before, during, and after vigorous activity.
  • Eat foods containing electrolytes, especially prior to exercising outdoors in hot weather.
  • Reduce or eliminate dehydrating substances such as alcoholic beverages and caffeine.
  • Avoid strenuous outdoor activity during the hottest times of day.
  • If you don’t have air conditioning at home, take advantage of cooling centers in your neighborhood.
  • If you live alone and are vulnerable, ask a neighbor or city official to look in on you periodically.

Heat cramps can quickly progress to more serious heat illness, which is characterized by the symptoms listed above.

If rest, hydration, and cooling down the body don’t alleviate heat cramps, see your doctor. Talk to a doctor immediately if your temperature doesn’t come down or your symptoms escalate.

Babies require follow-up medical attention for heat-related symptoms, even if they get better with at-home treatment.

Heat cramps can result from dehydration and electrolyte loss. Exercising or working in high temperatures can cause heat cramps. Babies, children, and older adults are more vulnerable to heat cramps than other age groups.

If you get heat cramps, rest, hydration, and stretching may help them to resolve.

Heat cramps can escalate to a more serious heat illness. Seek medical care or call 911 if at-home treatment doesn’t resolve the issue.