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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.

Stage G3b

In short

G3b means your eGFR has been 30–44 for more than 3 months. Everything on the G3a page still applies. At G3b more people need a potassium limit, the blood bicarbonate (acid balance) starts to matter, anemia becomes more common, and it is time to see a nephrologist if your risk of kidney failure is rising (KDIGO 2024). Many people still feel well, so the blood tests guide what to do.

Your numbers

Starting points, not your prescription

These numbers are typical starting points from guidelines. Your nephrologist, diabetes team and renal dietitian set your own numbers from your blood tests, urine output and medicines, and change them as your labs change. If your lab report or your team says something different, they win.

Starting numbers at G3b (70 kg adult with type 1 diabetes; the same as the app's "Suggest targets"):

Protein Potassium Phosphorus Sodium Fluid Energy
0.8 g/kg (about 56 g) review ceiling 3,500 mg, only if your blood potassium is high 1,000 mg, used when blood phosphate is high under 2,000 mg no set limit 30 kcal/kg (about 2,100 kcal)

Blood tests that matter more now

Test Typical (your lab's range wins) What your team watches for
Potassium about 3.5–5.1 mEq/L 6.0–6.4 "moderate"; 6.5 or more "severe"
Bicarbonate (CO2) 22 mEq/L or more; lower means acid is building up under 18: treatment is considered
Hemoglobin men 13 g/dL or more; women 12 g/dL or more below that is anemia; iron is checked first
Iron (TSAT and ferritin) – TSAT under 20 % with ferritin under 100 ng/mL means low iron stores; with anemia, KDIGO suggests iron at higher levels too (ferritin under 100 with TSAT under 40 %, or ferritin 100–299 with TSAT under 25 %)
Calcium and phosphate phosphate 2.5–4.5 mg/dL checked every 6–12 months
Test Typical (your lab's range wins) What your team watches for
Potassium about 3.5–5.1 mmol/L 6.0–6.4 "moderate"; 6.5 or more "severe"
Bicarbonate 22 mmol/L or more; lower means acid is building up under 18: treatment is considered
Hemoglobin men 130 g/L or more; women 120 g/L or more below that is anemia; iron is checked first
Iron (TSAT and ferritin) – TSAT under 20 % with ferritin under 100 µg/L means low iron stores; with anemia, KDIGO suggests iron at higher levels too (ferritin under 100 with TSAT under 40 %, or ferritin 100–299 with TSAT under 25 %)
Calcium and phosphate phosphate 0.81–1.45 mmol/L checked every 6–12 months

Sources: potassium range (MedlinePlus); potassium action levels (KDIGO 2024, Table 28); bicarbonate (KDIGO 2024 uses under 22 mmol/L for acid build-up, and practice point 3.10.1 for treatment); hemoglobin and iron (KDIGO 2026 anemia, recommendation 2.3); calcium and phosphate (KDIGO 2017). See Blood potassium, Bicarbonate and Hemoglobin and iron.

What changes now

Seeing a nephrologist. KDIGO lists reasons to be seen by kidney specialists, including a 5-year kidney failure risk (KFRE) above 3–5 %, an eGFR under 30, a lasting fall in eGFR of more than 20 %, a UACR of 300 mg/g (30 mg/mmol) or more with blood in the urine, a UACR above 700 mg/g, and problems with potassium, acid, anemia, bones or nutrition (KDIGO 2024, practice point 5.1.1 and Figure 48; ADA 2026 §11, recommendation 11.12a).

Potassium. Limit potassium only if your blood level runs high, and then with a renal dietitian (KDIGO 2024, practice point 3.11.5.1). The biggest wins are portion size, foods with potassium additives, and a few very high foods. About 90 % of potassium from additives is absorbed, so KDIGO advises limiting processed foods first (practice point 3.11.5.2). A day's limit, when one is needed, is often 2,000–3,000 mg (DaVita). With diabetes, high glucose and too little insulin also push potassium up (Sousa 2016).

Acid (bicarbonate). Failing kidneys keep more acid in the body. If your bicarbonate falls, your team may suggest tablets or, if your potassium allows, more fruit and vegetables. Treatment is considered when bicarbonate is under 18 mmol/L (KDIGO 2024, practice point 3.10.1).

Anemia. Low hemoglobin makes you tired and short of breath. Your team checks iron first, because iron deficiency is common and treatable (KDIGO 2026 anemia).

Protein with diabetes. Keep to about 0.8 g/kg a day (ADA 2026 §11, recommendation 11.3; KDIGO 2022, recommendation 3.1.1; KDIGO 2024, recommendation 3.3.1.1). KDOQI 2020 allows 0.6–0.8 g/kg with diabetes only under close supervision (KDOQI 2020, statement 3.0.2). This handbook and the app use 0.8 g/kg. Your dietitian decides with you. See Protein.

What to do

  • Ask for your latest potassium, bicarbonate and hemoglobin results, and write them down.
  • Ask what your KFRE is and whether you should see a nephrologist now.
  • If your potassium is high, ask for a renal dietitian appointment.
  • Check ingredient lists for "potassium chloride" and other potassium salts (Reading labels).
  • Do not use salt substitutes such as "lite salt" unless your kidney team says so: they contain potassium chloride (Morton; NKF).
  • Keep fruit and vegetables to ½-cup portions if you have a potassium limit (Potassium).
  • Keep glucose in range and never miss basal insulin: both affect potassium.
  • If you feel more tired or breathless than usual, ask for a hemoglobin and iron check.
  • Set your stage to 3b in the app: the potassium review ceiling becomes 3,500 mg (Targets and warnings).

Examples

Swaps that save potassium (USDA FoodData Central; NKF):

Instead of Potassium Try Potassium
½ cup orange juice about 248 mg ½ cup apple juice about 125 mg
1 small banana about 362 mg ½ cup blueberries about 57 mg
1 cup cantaloupe about 417 mg ½ cup cantaloupe about 208 mg
¼ tsp "lite" salt 350 mg herbs, lemon, garlic, pepper very little in the amounts used

Portion matters. "A large amount of a low-potassium food can easily turn it into a high-potassium food" (NKF). Half a cup of cantaloupe has half the potassium of a whole cup (USDA).

A low on a potassium limit. Treat it straight away. If orange juice is all there is, drink it: 4 oz is about 250 mg, which your day can absorb. Glucose tablets have none (Treating a low).

Ask your care team

  1. What is my KFRE? Should I see a nephrologist, and when?
  2. Is my potassium high enough to need a limit? What number should I aim for?
  3. What was my bicarbonate? Do I need treatment for it?
  4. Is my hemoglobin low? Have my iron levels been checked?
  5. Can I see a renal dietitian?
  6. Is 0.8 g/kg the right amount of protein for me?

Get help now if…

Call 911 (or your local emergency number)

Chest pain; severe breathlessness; fainting, a very slow or irregular pulse or sudden severe weakness, especially with a lab potassium of 6.5 mmol/L or more; a low the person cannot treat themselves (give glucagon, then call); possible DKA: blood ketones of 3.0 mmol/L or more, or any ketones with vomiting, deep fast breathing or fruity breath (2024 consensus). Full list: Get help now.

Call your care team today

A lab potassium of 6.0–6.4 mmol/L: KDIGO advises assessment in hospital if you feel unwell, otherwise a repeat test within 24 hours (KDIGO 2024, Table 28). Also vomiting, diarrhea or not eating (start your sick-day plan).

Sources

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