RDW 10.4 %

An RDW of 10.4 % is slightly below the typical 11.5–14.5% range, but a low RDW just means your red cells are very uniform in size. It is not linked to any disease and clinicians generally do not act on it if the rest of your CBC is normal.

A high RDW means your red blood cells vary in size more than normal — a mix of unusually small and unusually large cells. The most common causes are iron deficiency and vitamin B12 or folate deficiency, followed by recent blood loss, liver disease, red cell breakdown, or a recent transfusion. RDW cannot tell these apart by itself; the rest of your CBC and simple follow-up tests can.

Yes. RDW often rises before hemoglobin falls, so a high RDW with normal hemoglobin can be an early warning that iron, vitamin B12, or folate stores are running low. It can also follow recent blood donation or blood loss that your body is already correcting. A simple set of follow-up tests — usually ferritin, B12, and folate — can check for a developing deficiency before it becomes anemia.

Your result of 10.4 % is below the typical range, but this is one of the few lab values where 'low' is not a concern. It means your red cells are unusually consistent in size. Check that your hemoglobin and MCV are normal; if they are, no action is needed.

You lower RDW by treating whatever is causing it — there is no way to change RDW directly. If testing shows iron, B12, or folate deficiency, supplementing under your clinician's guidance corrects the RDW over roughly two to four months as new, uniform red cells replace old ones. RDW can even rise temporarily at the start of treatment as a wave of new cells enters the blood, so don't be alarmed by an early bump. Avoid starting iron pills on your own before testing — it can mask the real cause.

Both measure the same thing — variation in red cell size — but on different scales. RDW-CV is a percentage (typical adult range about 11.5–14.5%) and is what most US labs report as 'RDW.' RDW-SD is reported in femtoliters (fL), with a typical range of roughly 39–46 fL, and is less affected by the average cell size. If your report shows a number in the 40s with 'fL' next to it, you are looking at RDW-SD, and percentage-based ranges do not apply to it.

Almost never. The overwhelming majority of high RDW results are explained by iron, B12, or folate deficiency, blood loss, or chronic illness — not cancer. Research has linked higher RDW to worse outcomes in various diseases, but that makes it a general, non-specific marker of illness and inflammation, not a cancer test. In older adults with a persistently high RDW and other unexplained CBC abnormalities, clinicians may check for bone marrow disorders, which is one reason follow-up matters — but a high RDW by itself is not a reason to fear cancer.