RDW: The Test you didn't understand on your Blood Count

November 01, 2020

RDW: That test you don't understand on your Blood Count

Ever looked down on your blood count and not understood all the little acronyms and abbreviations down there? Well, time to learn about the newest and most important one, your RDW. Red Cell Distribution Width is the variability in the size of your red blood cells. We collect those when we do a blood count so it's an easy biopsy of what's going on inside. Now, red cells only live about 100 days. Did you know they predict how long you live? That's what the RDW does.

It was developed around investigating deficiencies in iron. With less iron, your red cells get smaller and smaller and your RDW goes up. If you have a hidden colon cancer and are losing iron, this tips you off. "Go get a colonoscopy!" I've said on numerous occasions. Turns out this was like the closet in the Narnia stories: you open it up and a whole new universe appears.

That was just the beginning. It's not just iron. The more we have looked and followed the RDW we have found that the variability revealed by the RDW predicts the "health" of your whole system and thereby how long you are going to live. Interestingly, the correlation with mortality in otherwise healthy older adults who don't have obvious underlying disease was even stronger in the largest metanalysis done to date. (11,827 adults from over seven different studies combined is a pretty good population sample.)

There must be something else going on. The first look has been to consider inflammation and basic disruption of your "oxidative stress". Examining selenium, A vitamins, E vitamins.... found that selenium the only was the only predictive deficiency of mortality with high RDW.

What about oxidative stress? Take a whole new look at the aging cell. With aging, many of our cells slide into senescence when we wanted them to be "quiescent". Quiescent means ready and waiting to go. Senescent means spiraling down and spitting out "oxidants", thereby altering our natural anti-oxidant response. When you reach a threshold of overwhelming your antioxidant response, you begin to run out of NAD. If you don't have sufficient NAD, you can't maintain your chromosomes and run proper cellular responses to other stresses. You get invaded by viruses more easily. Your immune system can't mount as vigorous a defense. And your RDW starts to rise.

Oh, my goodness! You get a peek into the very foundation of life, the health of your mitochondria with the RDW. This is a very simple test, not always exactly on the numbers (as you may, in fact, be short of iron) that suggests that you, the otherwise healthy individual, may be in trouble. Your level of senescent cells may be reaching that level of spiraling out of control. And all it took was a simple CBC with the conjunction of fabulous computer testing ability that can now measure the variability of your teeny, tiny little red cells. The standard, annual blood count gives you a fantastic little peek!

References: Clinical Nutrition, J Gerotol A BiolSci Med, Cell Metabolism,

Pop Quiz

1. What is the RDW?                     Answer: Red Cell Distribution Width

2. What was it first invented for?                            Answer: Smaller red cells and the distribution of red cell size that comes about with iron deficiency.

3. What simple supplement might help raise your RDW that you don't often get measured?          Answer: Selenium

4. What is RDW probably measuring in the majority of otherwise healthy adults?           Answer: the status of their mitochondria and their NAD+ availability.

5. What does RDW predict in otherwise healthy older populations?                  Answer: Mortality. A big one.