HomeArticlesBlood clots can be fatal - look out for the warning signs

Blood clots can be fatal – look out for the warning signs

Many people are dying preventable deaths from pulmonary embolisms or deep-vein thrombosis. Increased awareness can help reduce the toll.

Less than 20% of people know that blood clots in the legs or lungs are the third most common cause of cardiovascular deaths, according to Barry Jacobson from the University of the Witwatersrand’s Thrombosis and Haemostasis Research Unit.

“Most people only know about heart attacks and strokes … but too few people know about the third killer,” he said.

October 13 is World Thrombosis Day.

Jacobson said pulmonary embolism is the most preventable cause of hospital deaths in the world. Pulmonary embolism occurs when a blood clot travels from the legs, where it normally starts, to the lungs and becomes fatal.

According to the International Society for Thrombosis and Haemostasis, being in hospital for an extended period of time leads to more than two-thirds of all cases of blood clots in the leg.

“Too many doctors are not sensitised to diagnose and treat [blood clots] early enough in order to prevent embolism. Hence, many people are dying a preventable death,” he said.

Factors that increase the dangers

According to the society, the risk of blood clots is increased when people do not move for long periods of time – for example, when they have to stay in bed to rest or travel on long-haul air flights and don’t get up regularly to walk around.

Although accurate South African statistics are not available, in Europe alone half a million people die from blood clots each year – more than “the combined death total from Aids, breast and prostate cancer and highway accidents,” according to the society.

Jacobson said in South Africa there seems to be an increase in the occurrence of blood clots “related to the prevalence of HIV infection and tuberculosis [TB]”.

“Unfortunately, medication taken by those living with HIV and TB increases the risk of deep-vein thrombosis and consequential pulmonary embolism,” he said.

Increased risks for some women

Women have an “elevated risk of developing a potentially deadly blood clot in the leg or lungs if they are using oestrogen-based medication such as oral contraceptives and hormone replacement therapy, are pregnant or recently gave birth,” the society said on its website.

Jacobson said in the case of pregnancy, the body prepares itself for a “huge potential bleeding event” and a pregnant woman’s blood therefore becomes “more clottable so that the body can protect itself from bleeding uncontrollably”.

The potential for blood clots therefore increases.

In the case of oral contraceptives the body “tricks itself into thinking it’s pregnant in order to prevent pregnancy” and therefore increases blood clotting.

Age and obesity

Other risk factors, according to the society, include age (an 80-year-old is five to six times more at risk than a 40-year-old) and family history (if someone in your family has had a blood clot, you also could be at more risk); your risk becomes even higher if you also are in one of the trigger situations such as being in hospital, undergoing surgery or having to be on bed rest).

Additionally, obesity is a risk factor. There is a two to three times greater risk of fatal blood clotting, also known as venous thromboembolism, among people who are obese (with a body mass index higher than 30) compared with nonobese people.

The World Health Assembly has set a global target of reducing premature deaths from noninfectious disease, including cardiovascular disease, by 25% by 2025.


Symptoms of deep-vein thrombosis (a blood clot in a vein in your legs or arms) include:

  • Pain or tenderness starting in the calf;
  • Swelling of the leg, ankle or foot; and
  • Redness or noticeable discolouration of the leg and an unusual feeling of warmth in the limb.

Symptoms of pulmonary embolism include:

  • Unexplained shortness of breath;
  • Rapid breathing;
  • Chest pain (may be worse with deep breath);
  • Rapid heart rate; and 
  • Light-headedness or passing out.

How to prevent fatal blood clots

Incoming patients should be assessed for their risk of developing blood clots. But it is very important for patients to also be proactive.

In hospital: If you are going to have surgery or have to stay in hospital for other reasons, ask your doctor or healthcare professional three important questions:

  • What is my risk of developing a blood clot?
  • Should I receive some type of preventative medication for blood clots while I’m in hospital?
  • Should I also receive some type of preventative medication for blood clots once I’m discharged from hospital, and for how long?

In daily life:

  • If you experience any of the warning symptoms for a possible blood clot, seek medical attention immediately.
  • Move around as often as possible when travelling on long journeys where you are sitting for extended periods of time.
  • Maintain a healthy lifestyle and control your weight.

Sources: International Society of Thrombosis and Haemostasis; Thrombosis and Haemostasis Research Unit.

[Note this article was originally published on 13 October 2014]

Mia Malan is the founder and editor-in-chief of Bhekisisa. She has worked in newsrooms in Johannesburg, Nairobi and Washington, DC, winning more than 30 awards for her radio, print and television work.