Written by Joanna Jan, MD | Reviewed by Katie E. Golden, MD Updated on April 13, 2022
Key takeaways:
- Leg cramps and a blood clot in the leg can both cause pain in the calf muscle.
- There are some symptoms that help differentiate whether your pain is from a cramp or a blood clot.
- Leg cramps tend to go away on their own and are not harmful. But if you have a blood clot in your leg, it can be more serious and require medication to prevent further complications.
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Leg pain and cramping is common and often due to muscle spasms. While this pain can feel severe, it is usually not serious. But, sometimes, what feels like a leg cramp may actually be something more serious: a blood clot in your leg, also called a deep vein thrombosis (DVT). Here, we’ll review both conditions and provide some clues on how to tell the difference and what to do next. Promotion disclosureinfo_outlined
What are leg cramps, and what causes them?
A leg cramp — sometimes called a charley horse — is a painful muscle spasm. It happens when a leg muscle suddenly tightens up, usually for a brief period of time (a few seconds to minutes). This occurs most commonly in the calf muscle — also called the gastrocnemius — but can also happen in the muscles of the thighs or feet.
Leg cramps can have many different causes:
- Tired muscles
- Nerve damage due to neuropathy or trauma
- Electrolyte abnormalities, like low potassium or magnesium levels
- Kidney disease, which often affects electrolyte levels
- Dehydration
- Pregnancy
- Medical conditions that affect the blood vessels in the leg, such as peripheral artery disease or venous insufficiency
- Medications like diuretics for blood pressure, statins for cholesterol, and long-acting beta agonists for asthma
While there are many causes of leg cramps, most of the time it is not clear why they happen, and they often go away on their own.
What is a DVT, and what causes them?
A DVT occurs when our blood clots inside a vein. This more commonly occurs in the smaller veins that travel deep within the lower leg but can occur in other veins throughout the body, too.
You have an increased risk of developing a DVT for many different reasons:
- Immobilization: Anything that decreases the amount you use your legs can increase your risk of blood clot. This includes recent surgery, hospitalization, bedrest, or even prolonged travel like a long flight or road trip.
- Medical conditions: Certain conditions can make your blood more likely to clot. Some examples are inherited blood disorders, autoimmune disease, and cancer.
- Pregnancy: If you are pregnant or recently gave birth you are at higher risk, as increased estrogen levels affect the way that our blood clots.
- Medications: Birth control and hormonal replacement therapy increase the risk of blood clots.
What are the symptoms of a blood clot in your leg (DVT)?
A DVT does not always cause noticeable symptoms, and many people may not know they have one. In fact, up to 40% of people with DVTs may have no symptoms.
When symptoms are present, the most common ones include:
- Swelling. This may be visible just in the foot or below the knee, or it can affect the whole leg.
- Pain. People often describe a constant, dull pain in the calf, knee, or thigh.
- Redness of the skin. The redness is usually faint and diffuse.
- Warmth. When you touch the skin over the affected area, it may feel warmer than the rest of your skin.
Many times, these symptoms are only present in one leg. But sometimes a DVT (or multiple DVTs) can cause symptoms in both legs.
Many other conditions can cause these same symptoms, like cellulitis or lymphedema. So a DVT cannot be diagnosed by symptoms alone.
How to tell the difference between leg cramps and a DVT
While leg cramps and DVTs both cause calf pain (usually just in one leg), there are some differences that can help tell them apart:
- Timing: DVT symptoms are usually subtle at the start and then gradually increase over days. Cramps are the opposite. They typically start suddenly and feel severe but go away just as quickly and last only seconds to minutes. Cramps also most commonly occur in the middle of the night.
- Swelling: New leg swelling that is one-sided is more worrisome for DVT. Leg cramps can result from conditions that cause swelling (like kidney disease), but this swelling is typically normal and there all the time
- Warmth and redness: DVTs can cause noticeable redness and warmth in the leg, but this is much less common with cramps.
When should I worry about leg cramps?
While these symptoms may help you tell the difference between leg cramps and DVT, you should consider reaching out to your provider for help. No one expects you to make the diagnosis on your own. Here are a few more reasons you should see your provider for help:
- If your symptoms feel severe or are significantly impacting your daily activities.
- If you have new swelling, redness, or warmth in your leg that was not there before, as this is more suggestive of DVT.
- If you have risk factors for DVTs or blood clots.
Your provider may order blood tests or check an ultrasound of your veins if they think you may have a DVT.
Another reason to seek help if you’re unsure is that DVTs can lead to a more serious condition called pulmonary embolism (PE). This occurs when parts of the clot break off and travel to the lungs. It can cause symptoms like shortness of breath, chest pain, or fainting. This is potentially a life-threatening condition because it affects our oxygen levels and, sometimes, blood pressure. If you are experiencing any of these symptoms, it is best to see your provider or go to an emergency room for evaluation.
The bottom line
Leg cramps and DVTs can have similar symptoms. But there are some clues that can help you figure out if you should see your provider: DVTs typically cause one-sided leg swelling, redness, and warmth that worsens over time. Leg cramps tend to occur at night, come on suddenly, and get better after a few seconds or minutes. If you think you may have a DVT, or you’re not sure, your provider can help.
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