So do smoking, diabetes, homocysteine, the stickiness of your platelets, and, of course, your genes. The same holds true for fibrinogen, a soluble protein that can be transformed into stringy, insoluble fibrin, which forms the semi-solid base of blood clots.Ĭhronic inflammation increases the viscosity of blood. In men, a normal hematocrit is between 41% and 53%, meaning red blood cells account for 41%–53% of blood volume in women, it is between 36% and 46%.īlood fats such as low-density lipoprotein (LDL, 'bad' cholesterol) affect viscosity. Your hematocrit is a measure of both the number and the size of red blood cells. Red blood cells have the greatest influence on the blood's viscosity, since they account for up to half its volume.

How thick or thin your blood is depends on many factors. Red blood cells make up to half of the volume of blood.īlood is a complex soup (see 'What's in blood?'). The clear fluid known as plasma makes up blood's salty 'base.' It carries red and white blood cells, platelets, proteins, nutrients, hormones, dissolved gases, and wastes. Here's what we know about blood viscosity, how it might affect the heart and blood vessels, and what you can do to keep your blood flowing smoothly. It is strong enough, though, to keep viscosity in the back of your mind as another reason for drinking enough water and sticking with heart-healthy habits. Mind you, the evidence isn't nearly strong enough to put viscosity on a par with high cholesterol or blood pressure as heart hazards (although that didn't stop someone from writing The Blood Thinner Cure - more about that later). Extra-viscous blood may - emphasis on the may - also be a problem for the rest of us.

This is a concern for people with disorders such as polycythemia vera, in which the body makes too many red blood cells, or multiple myeloma, a type of cancer that creates too many white blood cells. The more viscous the blood, the harder the heart must work to move it around the body and the more likely it is to form clots inside arteries and veins. Viscosity measures a fluid's resistance to flow honey, for example, is more viscous than water. Some tantalizing threads of evidence suggest that people with thicker (or more viscous) blood have higher chances of developing heart disease or having a heart attack or stroke. For the heart and circulatory system, though, thinner, more watery blood might be better. The old adage 'Blood is thicker than water' makes sense for family ties. An interesting theory proposes that watering down your blood can prevent heart disease.

Thicker than Blood by Don Brobst