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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.

Reading your lab results

In short

Blood and urine tests show how well your kidneys filter and whether problems that kidney disease causes, such as high potassium or anemia, are starting. Each result has a number, a unit and the lab's normal range. One result is a snapshot. The trend over several tests tells you much more: KDIGO says an eGFR change of more than 20 % or a doubling of urine albumin is bigger than normal day-to-day noise and should be looked at (KDIGO 2024, practice points 2.1.3 and 2.1.5). Keep your results in one place and bring them to every visit.

How to read a lab report

Part of the report What it means Example
Test name Often shortened: K for potassium, Cr for creatinine, Hgb for hemoglobin, CO2 for bicarbonate "Potassium, serum"
Result Your number 5.3
Unit What the number is counted in. The same test can use different units in different countries mmol/L (the same number as mEq/L for potassium)
Reference range The range found in healthy people at that lab. Labs use different machines, so ranges differ a little 3.5–5.1
Flag H = high, L = low. Some labs mark a "critical" result and phone your doctor H
Date and time When the blood was taken. Compare results taken the same way, for example before dialysis 2026-09-14, 08:10
  1. Check the date, so you know you are looking at the newest result.
  2. Check the unit before you compare with a target. To switch units, see Units and conversions.
  3. Compare with the lab's own range printed next to it. Your lab's range wins over any range in this handbook.
  4. Compare with your last result. Is it going up, down or staying the same?
  5. Note anything that might have changed the result: an illness, a missed insulin dose, a big meat meal, hard exercise, your period, a new medicine. Each lab page lists what can fool that test.

Results bounce around a little even when nothing has changed. These are the changes guidelines treat as real:

Test A change worth asking about Source
eGFR a fall of more than 20 % from one test to the next KDIGO 2024, practice point 2.1.3
eGFR after starting an ACE inhibitor, ARB, finerenone or an SGLT2 inhibitor a fall of more than 30 %; a smaller dip is expected KDIGO 2024, practice points 2.1.4 and 3.6.4
UACR (urine albumin) doubling KDIGO 2024, practice point 2.1.5
Calcium, phosphate and PTH decisions are based on trends, not one value KDIGO 2017, recommendation 3.1.4
Potassium it can swing 0.24–0.73 mmol/L within one day, so a surprise result is often repeated KDIGO 2024, Table 25

Worked example. Your eGFR was 48. A drop to 44 is 8 % lower: within normal noise. A drop to 37 is 23 % lower: more than 20 %, so ask your team what changed. (Work it out: 48 − 37 = 11, and 11 ÷ 48 = 0.23, or 23 %.)

Which tests, and how often

These are minimum schedules from guidelines. Your team may test more often, especially after a medicine change or when a result is off.

Test Stage 3 (G3a–G3b) Stage 4 (G4) Stage 5 and dialysis Page
eGFR and UACR 1–4 times a year, depending on stage 1–4 times a year as your team decides; monthly blood tests on dialysis eGFR, UACR
Potassium with each kidney check, and 2–4 weeks after a new or bigger dose of an ACE inhibitor or ARB same monthly on dialysis Blood potassium
Calcium and phosphate every 6–12 months every 3–6 months every 1–3 months Phosphate, calcium and PTH
PTH depends on your first result every 6–12 months every 3–6 months same
Hemoglobin at least once a year at least twice a year at least every 3 months; at least monthly at US dialysis units Hemoglobin and iron
A1c twice a year; up to 4 times if not at goal or after a change same, but less reliable same, but unreliable A1c, CGM metrics

Sources: eGFR and UACR (ADA 2026 §11, recommendation 11.1b; KDIGO 2024, practice points 2.1.1–2.1.2); potassium after ACE inhibitors and ARBs (KDIGO 2024, practice point 3.6.2) and 4 weeks after starting finerenone (Kerendia label); calcium, phosphate and PTH (KDIGO 2017, recommendation 3.1.2); hemoglobin (KDIGO 2026 anemia, Figure 5; US dialysis units: 42 CFR 494.90); A1c (KDIGO 2022, practice point 2.1.1); monthly tests on dialysis (NIDDK).

Does age or sex change my numbers?

  • eGFR: yes. The equation uses your creatinine, age and sex, because creatinine comes from muscle and muscle mass differs by age and sex (NKF). The same creatinine of 1.4 mg/dL at age 60 gives an eGFR of about 43 for a woman and 58 for a man. Normal creatinine is also lower in women (MedlinePlus).
  • Anemia: yes. It starts below 13 g/dL in men and below 12 g/dL in women (KDIGO 2026 anemia).
  • Urine albumin: a little. Women pass less creatinine, so their UACR reads a bit higher for the same albumin (KDIGO 2024, Table 16).
  • Potassium and bicarbonate: hardly. Average potassium differs by 0.2 mmol/L or less by age and sex (KDIGO 2024, Table 24).
  • Food limits: no. Potassium, phosphorus and sodium limits do not change with age or sex. Age, sex, height and activity change your calorie needs, and being 65 or older can raise protein (design note 05). See Targets and warnings.
  • Pregnancy and children: different rules. The adult eGFR equations were not developed for pregnancy, so the app does not work out eGFR while you are pregnant (design note 05). Children use other equations (KDIGO 2024, practice point 1.2.4.3). Ask your specialist team; see Sex, fertility and pregnancy.

What to do

  • Ask for a copy of every result, or sign up for your clinic's patient portal.
  • Write each result on the tracker below or add it in the app, with the date.
  • Before a blood test, ask whether to fast. If creatinine is being checked, skip a big meat or fish meal for about 12 hours before if you can (KDIGO 2024, practice point 1.2.2.4).
  • At the blood draw, keep your hand relaxed: pumping your fist can make potassium read falsely high (KDIGO 2024, Table 25).
  • Bring the tracker to every visit and ask "What changed, and why?"
  • Track the trend, not one number. Your team decides treatment from several results.

In the app

Add results under Labs: potassium, phosphate, albumin, bicarbonate, UACR, creatinine, cystatin C, eGFR and A1c. The app converts units, keeps a history, shows a red alert for a potassium of 6.0 mmol/L or more, and may suggest that you review your food targets. It never changes your stage or your targets by itself (design note 05). See Targets and warnings and Reports for your care team.

A lab tracker to print

Fill in one row per test date. Use the units on your lab report and write them in the header.

Date eGFR UACR Potassium Phosphate Calcium PTH Bicarbonate Albumin Hemoglobin A1c or time in range
 
 
 
 
 
 

Ask your care team

  1. Which of my results are outside my lab's range, and do any need action?
  2. How has my eGFR changed over the last year, as a percentage?
  3. Which tests should I expect at my stage, and how often?
  4. Should I fast or avoid anything before my next blood test?
  5. Can I get my results through a patient portal?

Get help now if…

Call 911 (or your local emergency number)

A lab or your team tells you your potassium is 6.5 mmol/L or more (KDIGO 2024, Table 28), or you have chest pain, severe breathlessness, fainting or a very slow or irregular pulse (MedlinePlus). Full list: Get help now.

Call your care team today

A potassium of 6.0–6.4 mmol/L: KDIGO says get checked in hospital if you feel unwell, otherwise repeat the test within 24 hours (KDIGO 2024, Table 28). Also call if the lab or your team phones you about a result and you are not sure what to do.

Pages in this section

Sources

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