8 Signs of a Blood Clot You Should Never Ignore, According to Doctors

Feeling faint

“The lightheadedness is due in part to the chemical released from the lungs, changes in oxygenation of the blood, and in the blood pressure and heart rate,” Dr. Nelson says. “The brain is sensitive to changes in oxygen and to changes in blood flow.”

While it’s not an overly common symptom of a blood clot, it happens enough. One study published in the New England Journal of Medicine found that pulmonary embolisms were responsible for about 17% of hospitalizations for fainting in the 560 older people who were studied.