Included with every panel
Baseline labs come free with any panel you build.
Blood & iron
RDW test
Red cell distribution width. How much your red blood cells vary in size; can help pinpoint the cause of anemia and can flag early nutrient deficiencies. Included with every panel.
At a glance
In about 5 days
Most results are ready in about 5 days. Some specialty markers can take up to 21 days.
Check before your draw
This marker has no preparation tag, but it can still need preparation. Contact us before your draw if you’re not sure.
Walk in at Quest
Your lab order arrives by email. Most Quest locations take walk-ins, so bring it with a photo ID.
What it measures
RDW shows how much your red blood cells vary in size. When newer cells come out a different size from older ones, it can be an early clue to a nutrient shortage.
Why it matters for women
Low iron is very common in women because of periods and pregnancy, and RDW can rise early, sometimes before hemoglobin drops. Read with the size of your red cells, it can help show whether low iron, low vitamin B12 or folate, or a mix may be the cause.
You might check it if…
- your periods are heavy or last a long time
- you often feel tired even after a good night’s sleep
- you’re pregnant, planning to be, or recently gave birth
- you follow a vegetarian or vegan diet
What your result may mean
High RDW: what it may mean
A high RDW (red cell distribution width) may mean your red cells vary widely in size, and it can be an early clue to low iron, vitamin B12 or folate, or a mixed anemia. With periods and pregnancy, iron can run low, and RDW can rise before hemoglobin drops. Recent blood loss, a blood transfusion or liver disease can also widen it. Tiredness or pale skin may come from the reason behind it, not from RDW itself. Read with MCV, it can help a clinician sort out which nutrient or condition may be involved.
Low RDW: what it may mean
A low RDW may mean your red cells are very uniform in size, and a low or normal RDW may not be a concern on its own. This result can’t rule out anemia, since red cells can be small or large and still match one another. A normal RDW with a low MCV can fit thalassemia trait, an inherited blood difference that can be worth knowing about before pregnancy. A low RDW itself may cause no symptoms, so a clinician may focus on your hemoglobin and other red cell numbers.
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These notes provide context and do not diagnose a condition. Not yet available in NY, NJ, RI, HI, ND, SD or WV.