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.

Bicarbonate

In short

Bicarbonate is the body's main buffer against acid. On a lab report it may be called CO2, total CO2, TCO2 or HCO3 (MedlinePlus). Healthy kidneys remove acid every day. As kidney function falls below an eGFR of 60, acid builds up and bicarbonate starts to drop, most clearly at stages G4–G5 (KDIGO 2024). A low bicarbonate is linked with muscle loss and other problems, so your team may treat it with tablets or, if your potassium allows, more fruit and vegetables. A low bicarbonate on its own is not DKA. If you are ill, your ketone reading is the number that tells you about DKA.

Your numbers

Bicarbonate is the same number in mmol/L and mEq/L, so there is one table for both unit systems.

Result (mmol/L = mEq/L) What it means Source
about 22–29 the usual normal range (MedlinePlus lists 23–29; your lab's range wins) MedlinePlus
24–26 KDOQI says it is "reasonable" to keep bicarbonate here at stages 3–5 and on dialysis (expert opinion) KDOQI 2020, statement 6.1.3
under 22 low: common as kidney function falls KDIGO 2024
under 18 KDIGO says treatment should be considered KDIGO 2024, practice point 3.10.1
above your lab's upper limit while on treatment too much; treatment should not push it above normal KDIGO 2024, practice point 3.10.2

How common. Among people with diabetes, a bicarbonate under 22 was found in about 8 % at stage G3 with little urine albumin, rising to 38 % at stage G5 with a lot (KDIGO 2024).

How often. It is most often part of an electrolyte or basic metabolic panel, the same blood test that reports potassium and creatinine (MedlinePlus). Ask for the number if you do not see it on your report. On hemodialysis it is part of the monthly blood tests (NIDDK); compare results taken at the same point, for example before a session.

Age and sex. Average bicarbonate differs only slightly by age and sex (KDIGO 2024, Table 23). The treatment thresholds are the same for everyone.

Why it matters

Long-term acid build-up is linked with breakdown of protein and muscle, inflammation, and heart and other problems (KDIGO 2024). It also pushes potassium out of cells, so it can raise your potassium (Blood potassium). The evidence that treatment changes long-term outcomes is limited: in the BiCARB trial (300 people aged 60 or over with an eGFR under 30, not on dialysis, and bicarbonate under 22), bicarbonate tablets did not improve physical function or kidney function, cost more and caused more side effects (BiCARB trial; KDIGO 2024). That is why KDIGO frames treatment as preventing more severe acidosis, with 18 as the level to avoid.

How it is treated

Your team chooses the treatment. The options are:

  • Fruit and vegetables. At stages G1–G4 without dialysis, KDOQI suggests more fruit and vegetables to lower the acid load (KDOQI 2020, statement 6.1.1). Small trials found plant-rich diets worked about as well as bicarbonate tablets (KDIGO 2024). Only if your potassium allows: fruit and vegetables add potassium, so at stage G5 and on dialysis this is not the usual advice (design note 05).
  • Tablets. KDOQI recommends lowering acid with bicarbonate supplements at stages 3–5 and on dialysis (KDOQI 2020, statement 6.1.2). Sodium bicarbonate contains sodium, so your team watches your blood pressure, swelling and potassium (KDIGO 2024, practice point 3.10.2). This handbook does not give doses; your prescriber sets them.

A low bicarbonate is not DKA by itself

Diabetic ketoacidosis (DKA) is diagnosed when three things happen together (2024 consensus):

  1. high glucose (200 mg/dL, 11.1 mmol/L, or more) or known diabetes;
  2. ketones: blood ketones 3.0 mmol/L or more (or urine ketones 2+ or more);
  3. acid in the blood: pH under 7.3 and/or bicarbonate under 18 mmol/L.

With advanced kidney disease your bicarbonate may already be under 18 because of the kidneys. So the bicarbonate on a routine report cannot tell you whether you have DKA, and a low result does not mean you have it. When you are ill, have high glucose or missed insulin, check your ketones: they are the deciding number. Blood ketones of 1.6–2.9 mmol/L mean call your diabetes team now, and go to the emergency department if you cannot reach them quickly or you are vomiting; 3.0 or more means emergency care (NHS; ADA; Sick days). With kidney failure, ketone readings in DKA can be lower than usual, so symptoms such as vomiting, belly pain, deep breathing or drowsiness count even when the meter reads under 3.0 (2024 consensus, Table 4; JBDS 2022). A low bicarbonate does leave less buffer: ketoacidosis and diarrhea both lower bicarbonate further (MedlinePlus).

What to do

  • Find "CO2" or "bicarbonate" on your report and write it on your lab tracker.
  • If it is under 22, ask whether you need treatment and which kind.
  • Before adding fruit and vegetables, check your potassium and ask your team or dietitian (Potassium in food).
  • If you take bicarbonate tablets, tell your team about new swelling or higher blood pressure readings.
  • Keep blood ketone strips at home and use them when you are ill, whatever your bicarbonate.

In the app

Add a bicarbonate result under Labs. Under 22 the app shows a note that acid builds up as kidneys fail; it mentions fruit and vegetables only at stages 1–4 without dialysis, and asks you to check with your team first if your potassium is high. Under 18 it says KDIGO suggests considering treatment. Bicarbonate does not change your food targets (design note 05).

Examples

  • Stage G4, bicarbonate 19, potassium 4.6. Mia's team suggests more fruit and vegetables within her potassium budget and rechecks in 3 months.
  • Stage G4, bicarbonate 17, potassium 5.4. More fruit would add potassium, so Leo's team starts bicarbonate tablets and watches his blood pressure and swelling.
  • On hemodialysis, bicarbonate 20, vomiting since last night. Nora's routine bicarbonate is often around 20, so it tells her nothing new. She checks blood ketones: 2.1 mmol/L. Ketones with vomiting are an emergency, and on dialysis DKA can show lower ketone numbers, so her family takes her to the emergency department and calls her diabetes team and dialysis unit on the way (Sick days).

Ask your care team

  1. What is my bicarbonate (CO2), and is it low for me?
  2. Do I need treatment? Food, tablets or both?
  3. Is it safe for my potassium to eat more fruit and vegetables?
  4. If I take bicarbonate tablets, what should I watch for?
  5. How should I check for DKA when I am ill, given my kidney disease?

Get help now if…

Call 911 (or your local emergency number)

Blood ketones 3.0 mmol/L or more; ketones of 1.6 mmol/L or more with vomiting, or when you cannot reach your diabetes team quickly; or ketones with deep or fast breathing, fruity-smelling breath, drowsiness or confusion (NHS; ADA; 2024 consensus). See Get help now.

Call your care team today

Blood ketones 1.6–2.9 mmol/L without vomiting: call your diabetes team now, not later in the day (NHS). Also call for diarrhea, or new swelling or higher blood pressure after starting bicarbonate tablets (KDIGO 2024, practice point 3.10.2).

Sources

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