Type the reticulocyte result from your blood test — as a percentage or as an absolute count. You see it against the adult ranges MedlinePlus and Mayo Clinic Laboratories print, what they say moves it, and what the count says about how the bone marrow is answering iron or B12. Your lab’s own range, and your doctor, have the last word.
1.2% is
Inside MedlinePlus’s adult range of your red blood cells are reticulocytes
1.2%: inside the 0.77–2.26% MedlinePlus prints for healthy adults who are not anemic, and inside the 0.60–2.71% Mayo Clinic Laboratories prints for adults.
MedlinePlus: “The normal range depends on your blood level of hemoglobin. … The expected reticulocyte range is higher if hemoglobin is low from bleeding or from red cells being destroyed.”
That is inside the adult range MedlinePlus prints. The range on your own lab report — and your hemoglobin — are what your doctor reads it against.
What moves the number, in the sources’ words
- Normal value ranges may vary slightly among different laboratories.
After starting iron or B12
- MedlinePlus lists what the test is most often used for, including: “See if treatment for anemia is working”.
- Mayo Clinic Laboratories lists: “Monitoring early response to iron therapy or erythropoiesis-stimulating agents” and “Early monitoring of therapy for nutritional anemias (eg, megaloblastic, iron deficiency) where immature reticulocyte fraction precedes reticulocyte count increase by several days”.
- Neither prints how many days the count takes to change; the doctor who started the treatment decides when to re-test.
| Source | Percent | Absolute count |
|---|---|---|
| MedlinePlus | 0.77–2.26% | not printed |
| Mayo Clinic Laboratories | 0.60–2.71% | 30.4–110.9 × 10⁹/L |
This is not medical advice and it does not diagnose anything. It shows where a number sits against published ranges; what your result means for you depends on your lab, your hemoglobin, your other results, your history and your doctor.
MedlinePlus prints 0.77% to 2.26% as a normal reticulocyte count for healthy adults who are not anemic; Mayo Clinic Laboratories prints 0.60% to 2.71% for adults, and 30.4 to 110.9 × 10⁹/L for the absolute count. A result between the two percentages is inside one range and outside the other — and MedlinePlus says the expected range is higher when hemoglobin is low.
How to use it
Type the reticulocyte line from your lab report and say how it is printed: a percentage (“Retic 1.2 %”), an absolute count in × 10⁹/L or K/µL (“Absolute retic 55” — the same number either way), or in × 10¹²/L or M/µL (“0.055”, a thousand times smaller). You see where it sits against each adult range a source prints, the two percentages side by side, what the sources say moves the count, and what they say it shows after iron or B12 treatment. It does not diagnose anything: it places a number and quotes the sources.
What a reticulocyte count measures
MedlinePlus: “A reticulocyte count (retic count) measures the number of reticulocytes in your blood.” Reticulocytes are made in the bone marrow — “Then it sends them into your blood, where they mature into red blood cells within one to two days.” — so “A reticulocyte count checks to see if your bone marrow is making the right amount of red blood cells when old ones die off.” Mayo Clinic Laboratories puts it the same way: “The reticulocyte count is a measure of the number of red blood cells delivered by the bone marrow. It is elevated with active erythropoiesis such as regeneration and is decreased in hypoplastic or deficiency conditions such as vitamin B12 deficiency.”
The ranges the sources print
| Source | Percent | Absolute (× 10⁹/L) |
|---|---|---|
| MedlinePlus (review date 2/27/2026) | 0.77–2.26 | not printed |
| Mayo Clinic Laboratories (test RETB) | 0.60–2.71 | 30.4–110.9 |
MedlinePlus: “A normal result for healthy adults who are not anemic is 0.77% to 2.26%.” “The normal range depends on your blood level of hemoglobin.” “The expected reticulocyte range is higher if hemoglobin is low from bleeding or from red cells being destroyed.” “Normal value ranges may vary slightly among different laboratories.” Mayo Clinic Laboratories prints “Adults: 0.60-2.71%” and “Adults: 30.4-110.9 x 10(9)/L”, and separate ranges for children by age; this checker is for adults.
What raises or lowers it
MedlinePlus lists, for a higher than normal count: Anemia due to red blood cells being destroyed earlier than normal (hemolytic anemia); Bleeding; Blood disorder in a fetus or newborn (erythroblastosis fetalis); Kidney cysts or tumors, with increased production of a hormone called erythropoietin; Pregnancy. For a lower than normal count: Anemia caused by low levels of iron, vitamin B12, or folate; Bone marrow failure (for example, from a certain medicine, tumor, radiation therapy, or infection); Chronic kidney disease, due to decreased amounts of a key hormone called erythropoietin; Cirrhosis of the liver. Its lab-test page adds: “Your reticulocyte counts may be higher during pregnancy.” “You may have an increase in your count for a short time if you move to a place with a high altitude.” “Some medicines may increase or decrease your reticulocyte count.” And: “If your reticulocyte test results were not normal, it doesn’t always mean you have anemia or another health condition.”
After starting iron or B12
This is the question most readers of this site bring. MedlinePlus lists among the test’s uses: “See if treatment for anemia is working”. Mayo Clinic Laboratories lists “Monitoring early response to iron therapy or erythropoiesis-stimulating agents” and “Early monitoring of therapy for nutritional anemias (eg, megaloblastic, iron deficiency) where immature reticulocyte fraction precedes reticulocyte count increase by several days”. Neither source prints a number of days, or a count to aim for; the doctor who started the treatment reads the change against your earlier result. For the iron itself, see the Ferritin Level Checker; for B12, the Vitamin B12 Level Checker.
Worked examples
- 1.2% (the page’s example): inside both adult ranges.
- 0.7%: under MedlinePlus’s 0.77% and inside Mayo’s 0.60% — the two sources disagree, and the answer says so.
- 2.5%: above MedlinePlus’s 2.26% and inside Mayo’s 2.71%.
- Absolute 55 × 10⁹/L (or 55 K/µL): inside Mayo’s 30.4–110.9.
- 0.12 × 10¹²/L: 120 × 10⁹/L — above Mayo’s adult range.
Common mistakes
- Mixing the percentage and the absolute count. 1.2% and 55 × 10⁹/L can be the same blood; type the line with its own unit.
- Reading × 10¹²/L as × 10⁹/L. 0.055 × 10¹²/L is 55 × 10⁹/L.
- Reading the count without the hemoglobin. MedlinePlus ties the range to hemoglobin: it is higher when hemoglobin is low.
- Treating one source’s range as the only one. MedlinePlus and Mayo Clinic Laboratories print different adult percentages; your lab prints its own.
Frequently asked questions
What is a normal reticulocyte count?
MedlinePlus prints 0.77% to 2.26% for healthy adults who are not anemic; Mayo Clinic Laboratories prints 0.60% to 2.71% for adults, and 30.4 to 110.9 × 10⁹/L for the absolute count. Your lab’s printed range is the one your doctor uses.
What does a high reticulocyte count mean?
MedlinePlus lists hemolytic anemia, bleeding, kidney cysts or tumors that make more erythropoietin, and pregnancy; a move to high altitude can raise it for a while, and some medicines can too. It also says an abnormal result “doesn’t always mean you have anemia or another health condition”.
What does a low reticulocyte count mean?
MedlinePlus lists anemia caused by low levels of iron, vitamin B12 or folate, bone marrow failure, chronic kidney disease and cirrhosis of the liver. Mayo Clinic Laboratories says the count is decreased in “deficiency conditions such as vitamin B12 deficiency”.
What is a retic count?
The same test: MedlinePlus calls it “A reticulocyte count (retic count)”, a measure of the young red blood cells the bone marrow has just released.
Does the reticulocyte count go up after iron or B12?
Both sources list it as a way to see whether anemia treatment is working — Mayo Clinic Laboratories for “early response to iron therapy”. Neither prints how many days it takes; the doctor who started the treatment decides when to re-test.
What is the reticulocyte index?
Mayo Clinic Laboratories describes the traditional reticulocyte production index as “a value calculated from the reticulocyte percentage and hematocrit”; neither source prints the formula, so this checker does not compute one.
More blood-count checkers: the Red Blood Cell Count Checker, the Hemoglobin Level Checker and the Hematocrit Checker; for the iron panel, the TIBC Level Checker.
Read next
This is not medical advice, and nothing here diagnoses or treats anything. It shows where a number sits against published adult ranges and quotes what the sources say moves it; your lab’s own range, your hemoglobin, your other results and your doctor decide what it means. Some links on this site are affiliate links: I buy what I review at full price, and a commission never changes a verdict.