A low bicarbonate means acid is accumulating faster than your body can clear it.
The reflex is to replace the bicarbonate. The correct first move is to find out why it fell.
Metabolic acidosis symptoms
Most people with chronic metabolic acidosis feel nothing. It is found on a routine metabolic panel as a low CO2 or bicarbonate.
When it has been there for months or years, the signs are slow and easy to blame on something else:
- Tiredness that does not improve with rest
- Losing muscle and strength without trying
- Poor appetite and mild nausea
- Bone aches, or a fracture that seems out of proportion to the fall
Severe, sudden acidosis is different. Fast or deep breathing, vomiting, confusion, and extreme weakness need the emergency room, not a clinic visit. That picture usually comes with diabetic ketoacidosis, a serious infection, or a poisoning.
What a low bicarbonate on your labs means
On most lab reports, bicarbonate is listed as CO2 or total CO2. The normal range is roughly 22 to 29.
A value of 20 or 21 is easy to skip past. It is still worth a conversation if it shows up on more than one test, especially with kidney disease. A value under 18 should be looked at soon.
One lab number cannot tell you the cause. That takes the anion gap, which is calculated from the same panel, and sometimes a urine test.
The cause has to be established before the treatment
Metabolic acidosis is not one disease. The anion gap splits it into two families, and they have almost nothing in common.
A high anion gap means acid was added. Diabetic ketoacidosis. Lactic acidosis from sepsis or shock. Toxic alcohol ingestion. Kidney failure itself. Each of these is an emergency with its own treatment, and bicarbonate is rarely the answer.
A normal anion gap means bicarbonate was lost, or acid was not excreted. Diarrhea. Renal tubular acidosis. Certain medications. And chronic urinary retention — an obstructed bladder producing a normal-gap acidosis in a patient whose kidney function looks unremarkable, found only if someone thinks to look for it.
That last one is the point. A patient can be handed bicarbonate tablets for years while an obstructed bladder is quietly damaging both kidneys. Nobody checked a post-void residual. Nobody asked about the stream.
If your bicarbonate is low and nobody has calculated your anion gap, the diagnosis has not been made. Something is being treated, but nobody has said what.
Board-certified nephrology at Remix Medical in Houston. Call (713) 597-5131 or book online.
Common causes of metabolic acidosis
- Chronic kidney disease, usually once eGFR falls below about 45
- Long-lasting diarrhea, which drains bicarbonate out through the gut
- Renal tubular acidosis, where the kidney filters normally but cannot handle acid properly
- A bladder that does not empty, often from an enlarged prostate
- Medications such as acetazolamide and topiramate
- Uncontrolled diabetes (ketoacidosis), severe infection or shock (lactic acidosis), and toxic ingestions, which are emergencies
Then, once the cause is known
If chronic kidney disease is the cause — and it often is, as failing kidneys stop excreting the acid ordinary metabolism produces every day — the treatment does real work.
Correcting bicarbonate with oral sodium bicarbonate slows the progression of chronic kidney disease. Trials showed slower eGFR decline, less progression to dialysis, and better nutritional status. The intervention costs almost nothing.
And it is skipped constantly. A bicarbonate of 19 gets noted and left alone, because it produces no symptoms and looks minor next to the creatinine.
What chronic acid does while nobody treats it
The body neutralizes excess acid by pulling alkaline salts out of bone. Over years this demineralizes the skeleton, adding to a fracture risk already elevated in kidney disease.
Muscle is broken down to supply glutamine for acid excretion. The result is protein-energy wasting — the muscle loss common in advanced kidney disease, which independently predicts death.
Acidosis worsens hyperkalemia by driving potassium out of cells. It suppresses thyroid and growth hormone signaling. It contributes to insulin resistance.
And it accelerates the loss of kidney function itself, triggering ammoniagenesis and complement activation in the nephrons that still work.
Where the target sits
Serum bicarbonate at or above 22 mEq/L.
Not higher. Overcorrection causes volume overload from the sodium load, worsening hypertension, and metabolic alkalosis. In heart failure, the sodium in bicarbonate tablets demands real attention.
How metabolic acidosis is treated
Treatment depends on the cause, which is why the cause comes first.
- Emergencies like ketoacidosis or lactic acidosis are treated in the hospital by fixing what is producing the acid.
- Diarrhea-related acidosis improves when the diarrhea is treated.
- An obstructed bladder needs to be drained and the obstruction addressed.
- Acidosis from kidney disease is treated with sodium bicarbonate tablets, a change in diet toward more fruits and vegetables, or both, with a goal of 22 or higher.
Bicarbonate tablets are cheap and usually well tolerated. Bloating is the most common complaint, and the sodium matters for people with heart failure or hard-to-control blood pressure.
Diet
Meat and cheese produce acid. Fruits and vegetables produce base. Increasing plant foods lowers acid load and works.
It collides with the potassium restrictions many patients have been given — and that collision is usually resolved in favor of the restriction, without anyone examining whether the restriction was ever necessary.
| Base-forming (favor) | Acid-forming (limit) |
|---|---|
| Fruits and vegetables | Red and processed meat |
| Legumes | Excess cheese |
| Whole grains in balance | Refined, high-sodium foods |
What we do
Calculate the anion gap. Establish the mechanism before treating the number.
Look for the causes that hide: renal tubular acidosis, gastrointestinal loss, medications, and obstruction — including the post-void residual nobody measured.
Then, if chronic kidney disease is the driver, check bicarbonate at every visit once eGFR falls below 45, treat below 22, and watch sodium load, blood pressure, and volume.
A low bicarbonate is a finding, not a diagnosis. If yours was treated without being explained, the explanation is still worth having.
Call (713) 597-5131 or book online.