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Use this page to prepare questions for your care team. It does not replace their advice. Your own targets and doses come from your nephrologist, diabetes team and renal dietitian.

Hemoglobin and iron

In short

Hemoglobin (Hb, Hgb) is the protein in red blood cells that carries oxygen. Healthy kidneys make a hormone, erythropoietin (EPO), that tells the bone marrow to make red cells. With kidney disease there is less EPO and iron is harder to use, so anemia (low hemoglobin) is common: more than half of people at stages G4–G5 have it (KDIGO 2026 anemia). It can cause tiredness, shortness of breath, poor sleep, headaches and "brain fog". Treatment starts with finding and fixing causes, then iron, then sometimes an injection that replaces EPO (an ESA). Anemia and its treatment also change your A1c, so A1c can mislead (KDIGO 2022).

Your numbers

Test What the guideline uses
Hemoglobin: anemia under 13 g/dL in men; under 12 g/dL in women
Ferritin (iron stores) ng/mL
TSAT (iron available to make red cells) %
Low iron in body stores ("systemic iron deficiency") TSAT under 20 % with ferritin under 100 ng/mL, or under 200 ng/mL on hemodialysis
When KDIGO suggests starting iron, not on dialysis or on peritoneal dialysis ferritin under 100 ng/mL with TSAT under 40 %, or ferritin 100–299 ng/mL with TSAT under 25 %
When KDIGO suggests starting iron, on hemodialysis ferritin 500 ng/mL or less with TSAT 30 % or less
When routine iron is usually held ferritin over 700 ng/mL or TSAT 40 % or more
When an ESA is usually started, on dialysis Hb 9.0–10.0 g/dL or less
Hb target while on an ESA below 11.5 g/dL
Test What the guideline uses
Hemoglobin: anemia under 130 g/L in men; under 120 g/L in women
Ferritin (iron stores) µg/L (the same number as ng/mL)
TSAT (iron available to make red cells) %
Low iron in body stores ("systemic iron deficiency") TSAT under 20 % with ferritin under 100 µg/L, or under 200 µg/L on hemodialysis
When KDIGO suggests starting iron, not on dialysis or on peritoneal dialysis ferritin under 100 µg/L with TSAT under 40 %, or ferritin 100–299 µg/L with TSAT under 25 %
When KDIGO suggests starting iron, on hemodialysis ferritin 500 µg/L or less with TSAT 30 % or less
When routine iron is usually held ferritin over 700 µg/L or TSAT 40 % or more
When an ESA is usually started, on dialysis Hb 90–100 g/L or less
Hb target while on an ESA below 115 g/L

All from KDIGO 2026 anemia (definitions; recommendations 2.1, 2.3, 3.2.1 and 3.3.1; practice point 2.2). Not on dialysis, the Hb at which to start an ESA depends on your symptoms and on the risks of transfusion and of the ESA itself (recommendation 3.2.2).

Sex and age. The anemia thresholds differ by sex. Other cut-offs by age or ethnicity have been proposed, but the WHO thresholds above are the ones used in kidney studies (KDIGO 2026 anemia).

How often (KDIGO 2026 anemia, Figure 5 and practice points 2.5, 3.4.3.2–3.4.3.3):

Situation Hemoglobin checked at least
Stage G3 once a year
Stage G4 twice a year
Stage G5 and dialysis every 3 months; at US dialysis units, at least monthly (42 CFR 494.90)
Taking iron Hb, ferritin and TSAT every 3 months; every 1–3 months on hemodialysis
Starting or changing an ESA every 2–4 weeks, then at least every 3 months

Anemia testing includes a full blood count, reticulocytes, ferritin and TSAT (KDIGO 2026 anemia, practice point 1.2.1).

Causes your team looks for

Low EPO is not the only cause. KDIGO asks teams to fix correctable causes before starting an ESA (KDIGO 2026 anemia, practice point 3.1.2, Figure 8):

  • low iron, vitamin B12 or folate;
  • blood loss: from the gut, heavy periods, or during hemodialysis;
  • infection or inflammation;
  • not enough dialysis, or poor nutrition;
  • an underactive thyroid or a high PTH (Phosphate, calcium and PTH);
  • after a transplant, some anti-rejection and blood pressure medicines.

A very low ferritin (under 45 ng/mL) suggests bleeding somewhere, and may lead to a referral to a gut, gynecology or urology specialist (KDIGO 2026 anemia, practice point 1.2.3).

The treatment order

  1. Fix the causes above.
  2. Iron, as tablets or into a vein. On hemodialysis, iron into a vein is suggested. If tablets do not work after 1–3 months, or upset you, a switch to IV iron is reasonable. Iron is often paused during a serious infection (KDIGO 2026 anemia, recommendations 2.2 and 2.4; practice points 2.7–2.8).
  3. An ESA, if Hb stays low. The choice is shared with you, weighing your symptoms against risks such as stroke, heart problems and cancer. The target is below 11.5 g/dL: in trials, aiming higher brought more strokes, blood clots and high blood pressure (KDIGO 2026 anemia, practice point 3.1.1; recommendation 3.3.1).
  4. A blood transfusion only when the benefits outweigh the risks, judged by symptoms rather than a number. If you might have a transplant, transfusions are avoided when possible, because they can make your body form antibodies that make a match harder to find (KDIGO 2026 anemia, practice points 4.2 and 4.4).

This handbook gives no doses: your team sets them.

Anemia changes your A1c

Anemia, transfusions, ESAs and iron all make A1c read lower than your real average glucose, mostly at stages G4–G5 and on dialysis (KDIGO 2022; Pecoits-Filho 2016). Iron deficiency can make it read higher (JBDS–Renal Association; JBDS 2022). After any of these changes, judge your glucose by your CGM or meter, not A1c alone (A1c; CGM metrics).

What to do

  • Ask for your Hb, ferritin and TSAT and write them on your lab tracker.
  • Tell your team about tiredness, breathlessness, poor sleep or brain fog: these are treatable symptoms.
  • Tell your team about heavy periods, black stools or other bleeding.
  • If you take iron tablets, ask how to take them around meals and your other medicines, and tell your team if they upset your stomach or bowels: a switch to IV iron is an option (KDIGO 2026 anemia, practice point 2.7). Constipation also raises potassium (Blood potassium).
  • If you might have a transplant, ask your team to avoid transfusions when they can, and say so if you go into hospital.
  • After starting iron or an ESA, or after a transfusion, use your CGM to judge glucose, not A1c.

Examples

  • Low iron first. At stage G4, Lin's Hb is 10.8 g/dL, ferritin 60 ng/mL and TSAT 15 %. Her team starts iron tablets and checks again in 3 months.
  • On hemodialysis. Marcus's Hb has been 9.4 g/dL for two months even with good iron levels. He and his team talk through the benefits and risks of an ESA and decide to start it.
  • Waiting for a transplant. Jo is on the transplant list and needs surgery. She reminds the hospital team that she is a transplant candidate, so they avoid a transfusion if they can.
  • The A1c drop. Two months after starting an ESA, Pete's A1c fell from 7.9 % to 7.1 %, but his CGM average glucose had not changed. His team goes by the CGM.

Ask your care team

  1. Is my hemoglobin low for my sex? What is causing it?
  2. What are my ferritin and TSAT? Do I need iron, and tablets or IV?
  3. Would an ESA help my symptoms, and what are the risks for me?
  4. I might have a transplant. How do we avoid transfusions?
  5. Should we stop relying on my A1c now?

Get help now if…

Call 911 (or your local emergency number)

Chest pain, severe breathlessness, fainting, vomiting blood or material that looks like coffee grounds, black tarry stools or a lot of blood in your stool, or feeling dizzy from bleeding (MedlinePlus). After an iron infusion: trouble breathing, swelling of the face, lips or throat, or feeling faint, which can be signs of a reaction (KDIGO 2026 anemia, practice point 2.9). See Get help now.

Call your care team today

Small amounts of new bleeding, or much more tiredness or breathlessness than usual. During an iron infusion, tell the nurse at once about itching, flushing, breathlessness or feeling faint: these can be signs of a reaction, which the unit is set up to treat (KDIGO 2026 anemia, practice point 2.9).

Sources

Not yet reviewed by a clinician. Facts and sources last checked 2026-10-06.