Skip to content

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.

CGM metrics

In short

A continuous glucose monitor (CGM) shows how much of the day you spend in range, low and high. With advanced kidney disease, when A1c becomes unreliable, these numbers are the main way your team judges your glucose (KDIGO 2022; A1c). Look at the lows first: kidney disease makes lows more likely and harder to feel (JBDS–Renal Association). On dialysis, the makers of the main US sensors say not to use them, because they have not been tested in people on dialysis. Many dialysis teams still use CGM, and UK guidance recommends offering it (JBDS 2022). If you use one, treat it as a guide and check any low or surprising reading with a fingerstick meter.

Your numbers

Metric Goal for most adults Older or higher-risk adults
Time in range, 70–180 mg/dL more than 70 % (16 h 48 min a day) more than 50 % (12 h)
Time below 70 mg/dL less than 4 % (about 1 h) less than 1 % (about 15 min)
Time below 54 mg/dL less than 1 % (about 15 min)
Time above 180 mg/dL less than 25 % (6 h)
Time above 250 mg/dL less than 5 % (1 h 12 min) less than 10 % (2 h 24 min)
Glucose variability (CV) 36 % or less
Metric Goal for most adults Older or higher-risk adults
Time in range, 3.9–10.0 mmol/L more than 70 % (16 h 48 min a day) more than 50 % (12 h)
Time below 3.9 mmol/L less than 4 % (about 1 h) less than 1 % (about 15 min)
Time below 3.0 mmol/L less than 1 % (about 15 min)
Time above 10.0 mmol/L less than 25 % (6 h)
Time above 13.9 mmol/L less than 5 % (1 h 12 min) less than 10 % (2 h 24 min)
Glucose variability (CV) 36 % or less

Goals from the time-in-range consensus and ADA 2026 §6 (recommendations 6.3b–6.3c). Use 14 days of data with the sensor working at least 70 % of the time (time-in-range consensus; ADA 2026 §6, Table 6.2). Each 1 % of the day is about 15 minutes. Every 5 % more time in range brings real health benefits, so small steps count (time-in-range consensus). As a guide, 70 % in range goes with an A1c of about 7 %, and 50 % with about 8 %. The "older or higher-risk" column often applies with advanced kidney disease; ask your team which column is yours.

On dialysis, a different range may be used. UK dialysis guidance (2022) puts avoiding every severe low first, then avoiding time below 54 mg/dL (3.0 mmol/L). For people on insulin it proposes a higher target range of 108–216 mg/dL (6–12 mmol/L), with more than 70 % of the time in it (JBDS 2022). Your team decides which range your report uses.

Reading your AGP report, step by step

Most CGM apps can make an AGP (ambulatory glucose profile) report: a one-page, 14-day summary (time-in-range consensus).

  1. Check the data. Does it cover about 14 days, with the sensor active 70 % of the time or more? If not, the numbers may mislead.
  2. Read the time-in-ranges bar from the bottom up: very low (below 54 mg/dL, 3.0 mmol/L), low (54–69 mg/dL), in range, high (181–250 mg/dL) and very high (above 250 mg/dL, 13.9 mmol/L). Compare each with the goals above. Lows come first: fix them before chasing highs.
  3. Read the statistics: average glucose, GMI (an A1c-like number worked out from your CGM) and CV (how much your glucose swings; 36 % or less is the goal).
  4. Read the AGP curve. The middle line is your typical (median) glucose at each time of day; the shaded bands show how widely it varies. A band that dips below the low line at the same time most days is a pattern worth fixing.
  5. Look at the daily profiles at the bottom. Compare different kinds of days: dialysis days with non-dialysis days, work days with weekends, exercise days with rest days.
  6. Write down 1–3 questions for your visit, for example "Why am I low most afternoons after dialysis?"

Dialysis days on the report

  • Hemodialysis. Glucose tends to fall during a session; in one study the lowest point came in the third hour. In a CGM study, 3 in 4 lows happened within 24 hours of a session, and lows after dialysis are often not felt (JBDS 2022; JBDS–Renal Association). On the daily profiles this shows as a dip during or after your session times. UK guidance says glucose should be checked before and after dialysis for people on insulin (JBDS 2022).
  • Peritoneal dialysis. Glucose in the dialysis fluid is absorbed (often 400 calories a day or more) and can raise your glucose (DaVita). If you use icodextrin (Extraneal), some fingerstick meters read falsely high, even up to two weeks after stopping; use a glucose-specific meter, and ask whether your CGM is compatible (MHRA; Extraneal label).
  • Insulin on dialysis days is your team's job. Show them the pattern; never change doses on your own (Insulin and dialysis).

CGM accuracy on dialysis

  • What the makers say. Dexcom (G7) and Abbott (FreeStyle Libre 3 Plus and 2 Plus) say not to use their systems if you are on dialysis, because they have not been evaluated in people on dialysis and readings may be inaccurate (Dexcom G7 user guide; Abbott safety information). UK guidance notes that no CGM is licensed for dialysis and accuracy data are limited, yet recommends offering CGM to people on dialysis, for example when lows keep coming back or are not felt (JBDS 2022, recommendations 2.8–2.9). Use one on dialysis only with your team's agreement.
  • The time lag is longer. CGM measures glucose in the fluid under the skin, which trails blood glucose. That lag is longer in kidney failure, so a CGM can be late to show a low (JBDS–Renal Association). The 2016 UK guidance suggested starting a new sensor on a non-dialysis day, when sensors still needed fingerstick calibration.
  • Use a meter when in doubt. Both makers say to use a blood glucose meter when the sensor reading does not match how you feel (Dexcom G7 user guide; Abbott safety information). ADA says CGM accuracy should be confirmed with a meter when readings and the clinical picture do not match (ADA 2026 §7).
  • Things that can make sensors read falsely high, which can hide a low: hydroxyurea (Dexcom, Medtronic Guardian 4); acetaminophen (paracetamol: at any amount for Guardian 4, above 4 g a day for Dexcom); vitamin C above 500–1,000 mg a day, depending on the model (FreeStyle Libre); and mannitol or sorbitol given into a vein or in peritoneal dialysis fluid (Eversense 365) (ADA 2026 §7, Table 7.4; Abbott safety information). Check your own sensor's list and tell your team what you take.

What to do

  • Bring a 14-day AGP report to every diabetes and kidney visit.
  • Turn on low alerts, especially at night; most CGMs can alarm for lows and fast falls (KDIGO 2022).
  • Treat a low straight away, whatever the CGM says about the trend (Treating a low).
  • On dialysis, check a low or any surprising reading with a fingerstick meter, and check before and after each session if your team asks.
  • On peritoneal dialysis with icodextrin, use only a glucose-specific meter.
  • Mark your dialysis times so you and your team can compare dialysis and non-dialysis days (Dialysis days).

Examples

  • Reading the bar. Sam's report: 62 % in range, 6 % below 70 mg/dL and 2 % below 54. The lows are over goal (4 % and 1 %), so the first job is to reduce them, even though time in range is also below 70 %.
  • The post-dialysis dip. Ella's daily profiles show a drop to the low 60s mg/dL between 3 and 5 pm on Monday, Wednesday and Friday, after her morning sessions. She brings this to her diabetes team rather than changing anything herself.
  • The mismatch. On hemodialysis, Raj's CGM reads 95 mg/dL but he feels shaky and sweaty. His meter reads 58 mg/dL. He treats the low first, then reports the mismatch.

Ask your care team

  1. Which goals are right for me: the standard or the higher-risk column?
  2. Is my CGM accurate enough on dialysis, and when should I double-check with a meter?
  3. Does anything I take interfere with my CGM or meter?
  4. What pattern do you see on my dialysis days?
  5. Can my CGM data be shared with the clinic before visits?

Get help now if…

Call 911 (or your local emergency number)

A low the person cannot treat themselves: give glucagon if you have it, turn them on their side, then call. See Treating a low and Get help now.

Call your care team today

Lows that keep coming back, lows at night, or lows you no longer feel coming (ADA 2026 §6); time below 54 mg/dL (3.0 mmol/L) above 1 % on your report.

Sources

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