When a blood clot forms in a deep vein, it’s called deep vein thrombosis (DVT). These clots usually happen in the veins of the lower leg, thigh, or pelvis, but they can also develop in the arm. About 1 in 20 people get DVT over the course of their lifetime.
The medical term for a blood clot that starts in a vein is a “venous thromboembolism.” There are two types of these clots. DVT is one type. The other is a pulmonary embolism (PE). That’s a blood clot (usually a deep-vein clot) that travels to your lungs and blocks an artery there. It can be life-threatening.
The American Heart Association says that combined, DVT and PE affect between 300,000 to 600,000 people in the U.S. each year.
Is DVT More Common in Women or Men?
In general, DVT strikes slightly more men than women.
But if you’re a woman in your “childbearing” years, certain things can make you more likely than men to get DVT:
Pregnancy. For the first 6 weeks after you give birth, your chances for DVT (or PE) are higher. The risk is also higher than usual while you’re pregnant. Your risk goes up if you:
- Had DVT or PE in the past
- Have genes that make you more likely to get it
- Have a first-degree relative (like a parent or sibling) who’s had DVT or PE
- Are obese
- Can’t move much due to things like bed rest or long-distance travel
- Are pregnant with twins
- Are older
- Have a medical problem while pregnant, like cancer, a serious infection, or preeclampsia
Your doctor will work with you to lower your chances for deep-vein blood clots during and after pregnancy. For instance, if you’re at high risk for DVT, they may give you a blood-thinning medicine called an anticoagulant.
Hormonal birth control. Types that use estrogen can make you more likely to get dangerous blood clots. The risk goes up the most when you first start using estrogen-based contraceptives (birth control), which can include the pill, patch, shots, or a vaginal ring.
The risk is higher if you also:
- Inherited a blood-clotting condition
- Have close relatives who’ve gotten blood clots
- Are getting surgery
- Are obese
- Are traveling long-distance
If you’re using birth control, ask your doctor to help you weigh the benefits and risks. Some ways that you can lower your odds of getting a blood clot while using estrogen-based contraceptives are:
- Stay at a healthy weight
- Drink lots of water, especially during any long-distance travel
- Ask your doctor if you should wear graduated compression stockings (socks that put additional pressure on your lower legs)
Hormone therapy. If you get treatments for menopause symptoms that include estrogen, your chances of developing DVT or PE are generally low if you’re healthy and you don’t have other risk factors. Your risk goes up as you get older and if you also have health issues like:
- Heart disease
- A broken bone
- Renal disease
- Disorders that raise your odds for blood clots
If you’re thinking about getting hormone therapy, have your doctor weigh your risks and benefits before you start.
After menopause, a woman’s chances of getting DVT or PE are lower than a man’s.
Some research suggests that transgender women who get hormone therapy, especially estrogen, may be more likely to develop DVT and PE. One study links a specific type of lab-made estrogen called ethinyl estradiol with a higher risk for DVT and PE, compared with other forms of estrogen. The researchers also link the lab-made hormone progestin to a higher risk.
Does DVT Become More Common as You Get Older?
Yes. You can get deep-vein clots at any age, but it usually affects people who are older than 40. After 40, the risk for DVT and PE may double with each passing decade.
The exact reasons for that aren’t clear. One study looked at hospitalized people 60 and older. The researchers linked higher chances of getting a DVT or PE diagnosis to:
- Being a woman
- Receiving medicine or fluids through a small tube in a vein called a catheter
- Having cancer
- Staying in the hospital for a longer amount of time
- Getting hospitalized in summer and autumn (compared with spring)
Do Race and Ethnicity Play a Role?
In the U.S., African Americans have the highest rates of DVT and PE. Genetic factors play a role in creating our risk for DVT, and these factors seem to be more common among African Americans, the National Heart, Lung, and Blood Institute says.
In general, DVT and PE are less common in Asian Americans and Pacific Islanders.
One study of people in Oklahoma County, OK, found that the rate of new DVT and PE cases varied by race and ethnicity. The rate was highest for non-Hispanic Blacks, followed by non-Hispanic Whites, Native Americans, Hispanics, and lowest for Asian Americans and Pacific Islanders.