Dr. Kevin Casey explains the time lapse for DVT to form from bed rest.

How long might it take for a deep vein thrombosis to develop as a result of excessive bed rest?

“This is a little bit difficult to answer, but I will tell you that it is not long,” says Kevin Casey, MD, FACS, a vascular surgeon with West Coast Vascular.

“Our bodies are constantly in flux with changing hormones, cytokines and inflammatory markers.

“Under normal conditions the endothelium (vessel lining) provides a vasodilatory fibrinolytic environment.”

Vasodilatory fibrinolytic means suppression of clotting factors via dilation of blood vessels.

Dr. Casey continues, “This prevents coagulation [clotting], platelet adhesion, inflammation and clot formation.

“However, during states of disturbance of the endothelium, a cascade of prothrombotic [pro-clotting] and pro-inflammatory states occur, which can set the stage for amplification of the thrombotic process.  Inflammation and thrombosis are interrelated.”

Why don’t we get blood clots in our sleep?

“Depending on the other factors simultaneously occurring in a patient (i.e., major trauma, hypercoagulable state from malignancy, etc.), a DVT can form very quickly.

James Heilman, MD, CreativeCommons

“However, an average person lying in bed for two hours will usually not encounter this problem.”

A healthy person who has not had recent surgery or who does not have other risk factors for DVT such as being a smoker who’s on birth control pills, will not develop a DVT simply from sleeping overnight, seemingly immobilized for many hours.

  • The body actually moves during sleep in minute ways.
  • Muscles are innervated.
  • Subtle shifting occurs.

Air pressure is normal (as opposed to the cabin pressure in an airplane, which some experts believe contributes to increased DVT risk while on long flights).

Normal-length sleep is a required physiological process and thus, does not predispose one to a deep vein thrombosis.


If you develop a DVT from excessive bed rest, while still in bed, can getting up and about dissolve the clot?

“Possible, yes; likely, no,” says Dr. Casey.  “‘Getting up’ or ambulation doesn’t dissolve the clot.  But it will begin to release enzymes which prevent the pro-inflammatory state and propagation of the clot.

“Your body may either slowly dissolve or stabilize the clot after that.”

Dr. Casey specializes in vascular and vein therapy, and has been the lead researcher on publications examining abdominal aortic aneurysms, carotid artery disease and lower extremity critical limb ischemia.
Lorra Garrick has been covering medical, fitness and cybersecurity topics for many years, having written thousands of articles for print magazines and websites, including as a ghostwriter. She’s also a former ACE-certified personal trainer.