Skip to content
Blood Test Tracker

Reticulocyte Hemoglobin Content (CHr / Ret-He)

How much hemoglobin is in your newest red blood cells, in picograms (pg). It reflects the iron available to your bone marrow over the last few days.

AI-verified against cited sources. Awaiting expert reviewAlso called Ret-He, CHr, RET-HeLOINC 71694-4

Check your result

Sex (optional)

Type your result to see where it falls.

Nothing you type here leaves your browser.

What it is

Hemoglobin is the iron-containing protein that carries oxygen in red blood cells. Reticulocytes are red cells that have just left the bone marrow. This test measures how much hemoglobin is in an average reticulocyte. Because these cells are only a day or two old, the result reflects the iron your bone marrow had to work with over roughly the past 3 to 4 days. It is the same idea as MCH, but for your newest cells instead of all of them. Different analyzers use different names: Ret-He on Sysmex, CHr on Siemens ADVIA and RHe on Mindray.

Why it matters

Ferritin and transferrin saturation are the usual iron tests, but inflammation can make them hard to read. Reticulocyte hemoglobin is not changed by the short-term inflammatory response, so clinicians sometimes use it to see whether the bone marrow is getting enough iron. It also changes quickly after iron treatment starts, so it can show an early response. It is not a stand-alone test and is read together with ferritin, transferrin saturation, hemoglobin and MCV.

If it’s low

A low value means the newest red cells contain less hemoglobin than usual. That often reflects too little iron reaching the bone marrow, either because body iron is low or because inflammation is holding iron back. Conditions that reduce hemoglobin production, such as thalassemia, can also lower it. Your clinician reads it with ferritin, transferrin saturation, hemoglobin and MCV.

Common causes

  • Low iron stores, often from blood loss such as heavy periods or slow bleeding in the digestive tract
  • Not enough iron in the diet, or trouble absorbing iron
  • Iron held back by long-term inflammation and not reaching the bone marrow (functional iron deficiency)
  • Long-term kidney disease, especially with erythropoietin treatment, when iron demand can outpace supply
  • Thalassemia, including trait

What can help

  • Ask your clinician whether ferritin, transferrin saturation and a full iron panel should be checked
  • Ask whether the cause of any iron loss, such as heavy periods or bleeding in the stomach or bowel, should be looked into
  • Eat iron-rich foods such as meat, beans and leafy greens, and ask your clinician before starting an iron supplement

If it’s high

A value above your lab's range is uncommon, and it is not usually a sign of an iron problem. It can be seen when the newest red cells are larger than usual. Your clinician reads it together with your MCV and other results.

Common causes

  • Differences between analyzers and labs
  • Larger-than-usual red cells and reticulocytes (a higher MCV), as seen in some people with autoimmune hemolytic anemia

What can help

  • Ask your clinician how it fits with your MCV, vitamin B12 and folate
  • Compare it with the range printed by the same lab on earlier results

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

The usual range depends on sex and age. Choose women or men to see the one that applies.

Children and teens 8 ranges

See Ret-He by age and sex, with the U.S. survey numbers where they exist.

If this applies to you

Ret-He means a little more for some people. Open the one that fits you.

Low iron or anemia

Reticulocyte hemoglobin shows how much iron is reaching the newest red cells. BSG notes that a low value, once thalassemia trait is ruled out, is a sign of iron restriction, and that a rise on day 4 of iron treatment is an early sign of response.

Blood tests for low iron and anemia

What can affect your result

  • The analyzer: Ret-He, CHr and RHe are similar but not interchangeable
  • Iron treatment or erythropoietin treatment, which can change the value within days
  • Inherited hemoglobin conditions such as thalassemia
  • Age and sex: ranges differ in children, and some labs print slightly different adult ranges for men and women
  • Inflammation, which affects ferritin more than it affects this value
  • How long the blood sat before testing
  • Inherited conditions that lower hemoglobin production, such as thalassemia, can lower the value without iron deficiency.
  • Analyzer brand matters: Ret-He (Sysmex), CHr (Siemens ADVIA) and RHe (Mindray) are similar but not identical, and cutoffs are not interchangeable.
  • Recent iron treatment or erythropoietin treatment changes the value within days.
  • Samples are drawn into an EDTA tube. On one Sysmex analyzer, Ret-He was stable for at least 72 hours at room temperature or refrigerated, but each lab sets its own time limits.

A few days. It reflects the iron available to your bone marrow over roughly the past 3 to 4 days, and it can rise within 2 to 4 days of starting intravenous iron.

When to talk to a clinician

Labs don't usually publish an urgent-call limit for this result. Contact a clinician if a low value comes with tiredness, shortness of breath, dizziness, a fast heartbeat, pale skin, or heavy or long periods or other bleeding. Call 911 or your local emergency number for chest pain, severe shortness of breath, fainting or confusion.

Questions you could ask

  • How does this fit with my ferritin, hemoglobin and MCV?
  • Could my red cell size (MCV), vitamin B12 or folate explain a high result?
  • Could low iron, or iron that isn't reaching my bone marrow, explain this?
  • Should we check ferritin and transferrin saturation alongside it?
  • If I'm treated for low iron, when should we recheck this?

Questions people ask

How is this different from ferritin?

Ferritin mostly reflects the iron you have stored, and it can rise with inflammation even when iron is short. Reticulocyte hemoglobin reflects the iron your bone marrow has used in the last few days to make new red cells, and inflammation affects it less. Clinicians usually look at both.

My report says CHr, Ret-He or RHe. Are they the same?

They measure the same idea, hemoglobin in your newest red cells, on different analyzers. Studies show CHr and Ret-He give essentially similar results, but the cutoffs are not identical between brands. Use the range printed on your report.

Can it change quickly with iron treatment?

Yes. It can rise within a few days of starting iron, which is why clinicians sometimes use it to see whether treatment is reaching the bone marrow. Your clinician decides when to repeat it.

Show the science and sources

Is a change real?

Ret-He naturally varies about 1.92% from test to test in the same healthy person. Between two results from the same lab, a change of roughly 6% or more is unlikely to be day-to-day noise or lab variation (95% reference change value). Source: Systematic review and meta-analysis of within-subject and between-subject biological variation estimates of 20 haematological parameters (Coskun A et al., EFLM WG-BV).

For clinicians and researchers

Reticulocytes mature for 1 to 3 days in the marrow and circulate for 1 to 2 days, so reticulocyte hemoglobin content (CHr on Siemens ADVIA, Ret-He on Sysmex, RHe on Mindray) is an indirect measure of the functional iron available for hemoglobin synthesis over the previous 3 to 4 days (Am J Hematol 2008). It rises within 2 to 4 days of starting intravenous iron and is an early indicator of iron-restricted erythropoiesis during erythropoietin therapy (Am J Hematol 2008; Crit Rev Clin Lab Sci 2000). It is not affected by the acute-phase response, unlike ferritin and transferrin saturation (Urrechaga 2026). Diagnostic cutoffs depend on the population and analyzer: a 140-patient hemodialysis cohort found CHr below 32.4 pg identified iron deficiency defined by ferritin and transferrin saturation (Int J Lab Hematol 2008); studies cited by Urrechaga 2026 reported CHr 30.5 pg (ADVIA; sensitivity 93%, specificity 69% for iron deficiency anemia, with bone marrow iron as the reference, in anemic adults over 60) and, in a separate study, Ret-He 26.0 pg (Sysmex; sensitivity 85%, specificity 69%); in a 211-patient study, Ret-He had an area under the curve of 0.902 for iron deficiency defined by ferritin below 12 ng/mL (Toki 2017). Thalassemias and thalassemic hemoglobin variants also lower Ret-He, MCH and MCV (Int J Lab Hematol 2012; Clin Lab 2021), so a low value is not specific to iron. Higher MCV was associated with higher Ret-He in warm autoimmune hemolytic anemia (Ann Clin Lab Sci 2021). CHr and Ret-He produce essentially similar results (Int J Lab Hematol 2012), but analytical differences between manufacturers still limit universal cutoffs, and ICSH and ISLH working groups are addressing harmonization (Urrechaga 2026). Reference limits shown are adult limits from Mayo Clinic Laboratories (30.0–37.6 pg), Vanderbilt (men 29.8–40.4, women 30.1–39.8), OHSU (29–38) and QEHB (25.9–38).

LOINC 71694-4 (primary), 42810-2. Specimen: whole-blood.

Sources

  1. Reticulocyte Profile, Blood (test RETB), Mayo Clinic Laboratories (catalog mirror at testcatalog.org)
  2. Sysmex Complete Blood Count Reference Ranges (March 2024), Vanderbilt Medical Laboratories (2024)
  3. Heme Reference Ranges (updated 6/5/18), OHSU Laboratory Services (Oregon Health & Science University) (2018)
  4. Haematology Adult Reference Ranges (HAE.N002, PUB_040), QEHB Pathology (2026)
  5. Reticulocyte hemoglobin content, American Journal of Hematology (2008)
  6. Reticulocyte cellular indices: a new approach in the diagnosis of anemias and monitoring of erythropoietic function, Critical Reviews in Clinical Laboratory Sciences (2000)
  7. The Role of Reticulocyte-Derived Parameters in the Detection of Iron-Restricted Erythropoiesis in the Elderly, Diagnostics (Basel) (2026)
  8. Evaluation of reticulocyte haemoglobin content as marker of iron deficiency and predictor of response to intravenous iron in haemodialysis patients, International Journal of Laboratory Hematology (2008)
  9. Reticulocyte hemoglobin equivalent as a potential marker for diagnosis of iron deficiency, International Journal of Hematology (2017)
  10. Reticulocyte hemoglobin equivalent to detect thalassemia and thalassemic hemoglobin variants, International Journal of Laboratory Hematology (2012)
  11. Discrimination of Iron Deficiency, Alpha and Beta Thalassemia on the Basis of Red Cell Distribution Width and Reticulocyte Indices, Clinical Laboratory (2021)
  12. Reticulocyte Hemoglobin Equivalent in Patients with Idiopathic Warm Autoimmune Hemolytic Anemia: Implication in the Development of Macrocytosis, Annals of Clinical and Laboratory Science (2021)
  13. Stability of New Erythrocyte and Reticulocyte Parameters in Testing for Anemia on the Sysmex XN 9000, Laboratory Medicine (2018)

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

Related markers