Several months ago I posted a blog that reviewed what physicians knew about the relationship between Covid 19 illness and the strange development of blood clots in both the arteries and veins of some people who contract the virus.

While we still do not know exactly why some people are predisposed to having a more severe form of Covid 19 (obesity, diabetes, underlying lung and heart disease) we have learned a bit more with respect to the relationship of Covid 19 and formation of blood clots.

In the past, virtually all blood clots in the lungs, called pulmonary emboli, actually formed first in veins of the legs or pelvis and then traveled or “broke off”, finding their way through the heart into the lungs.  It now appears that in Covid 19 patients, blood clots which lodge in the small vessels of the lung, do not originate from the legs or pelvic veins.  Interestingly, the virus appears to cause a local inflammation of the lung blood vessels themselves.  It is the inflammation of these delicate blood vessels that seems to result in the local development of blood clots which are then responsible for the low oxygen levels seen in very ill Covid 19 patients. While blood clots can still form in the legs and pelvis of Covid 19 patients, it appears that a lot of the Covid 19 lung issues are caused by blood clots that form within the lung itself and not elsewhere.

Blood thinner medications are now given to ALL Covid 19 patients sick enough for hospital admission regardless of presence of blood clots.  And the dose of these blood thinners is adjusted upwards depending on the severity of illness.  This practice has been shown to be one of the most successful therapies for hospitalized Covid 19 patients.  Along with steroids, such as dexamethasone, these two inexpensive medications have dramatically reduced the chance of dying in a hospital from Covid 19.

What is also clear is that there is no advantage or need to take any type of blood thinner for the Covid 19 patient who is not hospitalized.  This even includes aspirin unless already taking it for another indication.  Finally, when a Covid 19 patient leaves the hospital, the risk of blood clots forming in the lungs decreases so much that most patients do not need to continue their blood thinner medications at home.


As we learn more about Covid 19, I will keep you updated.