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Draft: not yet reviewed by a clinician

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.

A1c

In short

A1c (HbA1c) shows your average glucose over the last 2–3 months, by measuring how much glucose has stuck to the hemoglobin in your red blood cells (NIDDK). Up to stage G3b it works well. At stages G4–G5 and on dialysis, KDIGO calls it unreliable (KDIGO 2022, practice point 2.1.2): anemia and its treatment push it down, and acid build-up and some lab methods push it up. Then your CGM report is the better guide (CGM metrics). Never judge your safety from A1c alone: a "good" A1c can hide frequent lows.

Your numbers

A1c
Without diabetes below 5.7 %
Goal for many adults with diabetes (ADA) below 7 %
KDIGO goal with CKD, not on dialysis set for you, from below 6.5 % to below 8.0 %
On dialysis no agreed goal; UK guidance says use A1c with caution, and over 9.5 % usually means high glucose unless iron is very low
Before a planned pregnancy, ideally below 6.5 %, if reached without problem lows
A1c
Without diabetes below 39 mmol/mol
Goal for many adults with diabetes (ADA) below 53 mmol/mol
KDIGO goal with CKD, not on dialysis set for you, from below 48 to below 64 mmol/mol
On dialysis no agreed goal; UK guidance says use A1c with caution, and over 80 mmol/mol usually means high glucose unless iron is very low
Before a planned pregnancy, ideally below 48 mmol/mol, if reached without problem lows

Sources: without diabetes (NIDDK); ADA goal (ADA 2026 §6); KDIGO goal (KDIGO 2022, recommendation 2.2.1, which covers people not on dialysis); dialysis (JBDS 2022, recommendations 2.1–2.2); pregnancy (ADA 2026 §15, recommendation 15.3). A lower goal is not better if it brings more lows. Your team sets your goal from your low risk, your stage and how you feel.

Converting. mmol/mol = (% − 2.15) × 10.929 (NGSP).

% 6.0 6.5 7.0 7.5 8.0 9.0
mmol/mol 42 48 53 58 64 75

How often. Twice a year is reasonable when you are stable and at your goal; up to 4 times a year if you are not at goal or your treatment changed (KDIGO 2022, practice point 2.1.1; ADA 2026 §6).

How reliable at each stage (KDIGO 2022, Figure 11):

Stage A1c reliability CGM glucose management indicator (GMI)
G1–G3b high occasionally useful
G4–G5, dialysis or transplant low likely useful

Why A1c misleads in advanced kidney disease

Makes A1c read lower than your real average Makes A1c read higher
Anemia and red cells that live a shorter time (KDIGO 2022) Acid build-up and inflammation (KDIGO 2022, Figure 10)
A recent blood transfusion (KDIGO 2022; ADA 2026 §6) Carbamylated hemoglobin from waste build-up, on some lab methods (JBDS–Renal Association; Pecoits-Filho 2016)
An ESA (EPO injection) or iron treatment (KDIGO 2022) Iron deficiency (JBDS–Renal Association)

Recent blood loss, hemoglobin variants such as sickle cell trait, and pregnancy can also make A1c inaccurate (NIDDK; ADA 2026 §6). UK guidance (2016) asked dialysis units to know which A1c method their lab uses, because some methods read carbamylated hemoglobin as A1c (JBDS–Renal Association).

What to use instead

  • CGM time in range and GMI. KDIGO says CGM metrics such as time in range and time in low "may be considered as alternatives" to A1c, and GMI can be used when A1c does not match your meter or symptoms (KDIGO 2022, practice points 2.1.3 and 2.2.2). If your A1c is lower than your GMI, the A1c is probably reading low by about that difference. Recheck the comparison over time, because it can drift (KDIGO 2022). A time in range of 70 % goes with an A1c of about 7 % (time-in-range consensus).
  • Fructosamine and glycated albumin reflect the last 2–4 weeks (ADA 2026 §6). ADA calls them "helpful" in advanced CKD (ADA 2026 §11). KDIGO found no proven advantage over A1c, and both can be thrown off by low blood albumin, protein in the urine or peritoneal dialysis (KDIGO 2022). UK dialysis guidance (2022) says there are not enough data to use them on dialysis, and that on peritoneal dialysis they may be less reliable than A1c (JBDS 2022, recommendations 2.3 and 6.2). Ask which your team uses.

What to do

  • At stage 4–5 or on dialysis, ask your team to judge your glucose mainly by CGM, not A1c alone.
  • Bring a 14-day CGM report to every visit (CGM metrics).
  • If you start an ESA or iron, or have a transfusion, expect A1c to read lower than your real average for a while (Hemoglobin and iron).
  • If your A1c looks "too good" but you have many lows or high readings, tell your team.
  • For the log: record meals, carbohydrate and the CGM pattern around them. In advanced kidney disease your team may set goals from CGM metrics such as time in range rather than A1c, and reviews your meter or CGM data at each visit (KDIGO 2022, practice point 2.2.2; JBDS 2022, recommendation 2.6).
  • Planning a pregnancy? Goals are tighter and the plan is made with specialists before you try: a maternal-fetal medicine specialist with your kidney and diabetes teams (Sex, fertility and pregnancy).

In the app

You can add A1c results under Labs. A1c and CGM readings do not change your food targets; the app adds a note that A1c is less reliable in advanced kidney disease (design note 05).

Examples

  • The low that A1c hid. On hemodialysis, Jordan's A1c is 6.4 %. His CGM shows a GMI of 7.6 % and 6 % of the time below 70 mg/dL. The A1c is reading low, and the lows matter more than the A1c. His team works on the lows first.
  • After an ESA. Two months after starting an ESA, Pat's A1c fell from 7.9 % to 7.1 %, but her CGM average was the same. Nothing about her glucose had changed.
  • Stage G3a. Ana's A1c is 7.4 % (57 mmol/mol) and matches her GMI of 7.3 %. At her stage A1c is still reliable, and she and her team agree a goal of under 7.5 %.

Ask your care team

  1. Is my A1c still reliable at my stage?
  2. What is my GMI, and how does it compare with my A1c?
  3. Should we use my CGM report, fructosamine or glycated albumin instead?
  4. What A1c or time-in-range goal is safe for me, given my risk of lows?
  5. Does my lab's A1c method read carbamylated hemoglobin?

Get help now if…

A1c is never urgent by itself. Lows and high glucose with ketones are.

Call 911 (or your local emergency number)

A low the person cannot treat themselves (give glucagon, then call), or blood ketones of 3.0 mmol/L or more, or ketones with vomiting. See Treating a low and Get help now.

Call your care team today

Lows that keep coming back or that you no longer feel; high glucose with ketones of 1.6–2.9 mmol/L (call now, and go to the emergency department if you cannot reach your team quickly or you are vomiting (ADA)); not eating (Sick days).

Sources

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