Bicarbonate is your body’s primary chemical buffer, keeping your blood at a stable pH between 7.35 and 7.45. It neutralizes acids as they’re produced, helps transport carbon dioxide from your tissues to your lungs, and plays a key role in digestion. Without it, normal metabolism would make your blood dangerously acidic within minutes. Here’s how it works and why it matters.
How Bicarbonate Keeps Your Blood Balanced
Every time your cells burn glucose for energy, they produce carbon dioxide as a byproduct. That carbon dioxide dissolves in your blood and reacts with water to form carbonic acid, which would steadily lower your blood pH if left unchecked. Bicarbonate acts as a chemical sponge for that acid: it binds to the excess hydrogen ions (the particles that make something acidic) and converts them back into carbon dioxide and water, which you then breathe out through your lungs.
This system is remarkably efficient because it’s “open,” meaning your lungs can remove carbon dioxide continuously. If your blood starts getting too acidic, you breathe faster and blow off more carbon dioxide, shifting the balance back toward normal. If your blood gets too alkaline, your breathing slows, retaining more carbon dioxide to bring pH back down. The kidneys fine-tune this process over hours and days by adjusting how much bicarbonate they keep or discard. Together, your lungs and kidneys maintain a buffering capacity of about 75 millimoles per liter of blood at normal pH.
Transporting Carbon Dioxide
About 80% of the carbon dioxide your tissues produce travels through your bloodstream in the form of bicarbonate. When carbon dioxide leaves your cells and enters nearby blood vessels, an enzyme inside red blood cells rapidly converts it into bicarbonate ions. Those ions dissolve easily in plasma and travel to the lungs, where the reaction reverses: bicarbonate turns back into carbon dioxide gas, which you exhale. The remaining carbon dioxide either stays dissolved in plasma (about 10%) or binds directly to hemoglobin (another 10%).
What Your Kidneys Do With Bicarbonate
Your kidneys filter bicarbonate out of the blood constantly, then reabsorb almost all of it to keep levels stable. About 70 to 80% of that reabsorption happens in the first segment of the kidney’s filtering tubes (the proximal tubule), with the rest recovered further along. The mechanism is the same throughout: kidney cells pump hydrogen ions into the urine, where they react with bicarbonate to form carbon dioxide and water. That carbon dioxide slips back into the kidney cell, gets converted into fresh bicarbonate, and returns to the bloodstream.
This recycling process also lets your kidneys generate brand-new bicarbonate when your body needs extra buffering. They do this by breaking down the amino acid glutamine, which produces two bicarbonate molecules for every glutamine processed. This becomes especially important when acid levels are high, such as during prolonged fasting, intense exercise, or kidney disease.
Bicarbonate in Digestion
Your stomach releases strong hydrochloric acid to break down food, but that acid would damage the lining of your small intestine if it arrived unchecked. The pancreas solves this by secreting 2 to 3 liters of bicarbonate-rich fluid per day into the upper small intestine. This alkaline juice neutralizes stomach acid on contact, creating the right environment for digestive enzymes to work. It also flushes those enzymes through the pancreatic duct so they don’t start digesting the pancreas itself.
What Happens When Levels Drop Too Low
A normal blood bicarbonate level falls between 23 and 29 millimoles per liter. When it drops below that range, a condition called metabolic acidosis develops. The four most common causes are uncontrolled diabetes (where acidic compounds called ketones build up), severe diarrhea (which drains bicarbonate directly from the gut), lactic acidosis (from liver failure, low blood sugar, or extreme exercise), and kidney disease that prevents the kidneys from clearing enough acid. Diarrhea and kidney failure are the two most frequent triggers overall.
Symptoms of low bicarbonate are often vague at first: fatigue, nausea, rapid breathing as your lungs try to compensate. As it worsens, confusion and dangerously low blood pressure can develop. In chronic kidney disease, guidelines recommend oral bicarbonate supplements when blood levels fall below 22 mmol/L, with a target of 24 to 26 mmol/L to help slow further kidney damage.
What Happens When Levels Rise Too High
Excess bicarbonate pushes blood pH above normal, a state called metabolic alkalosis. This can happen from prolonged vomiting (which removes stomach acid faster than the body can replace it), overuse of antacids, or certain hormone imbalances. Symptoms include confusion, lightheadedness, hand tremors, nausea, numbness or tingling in the face and hands, and muscle twitching or prolonged spasms. Severe cases can progress to stupor or coma.
Sodium Bicarbonate as a Sports Supplement
During high-intensity exercise, your muscles produce large amounts of acid that contribute to the burning sensation and fatigue you feel near your limit. Taking sodium bicarbonate (essentially baking soda) before exercise raises blood bicarbonate levels, giving your body extra buffering capacity to soak up that acid.
The optimal dose is 0.3 grams per kilogram of body weight, taken before exercise. For a 70-kilogram (154-pound) person, that’s about 21 grams. Doses as low as 0.2 g/kg can still improve performance, while going higher than 0.3 g/kg doesn’t add benefit and increases the likelihood of gastrointestinal side effects like bloating, nausea, and diarrhea. The performance boost shows up most clearly in activities lasting 1 to 7 minutes at high intensity: swimming, rowing, cycling sprints, combat sports, and middle-distance running.
Bicarbonate in Medical Treatment
In hospital settings, intravenous sodium bicarbonate is used for severe metabolic acidosis when blood pH drops below 7.0, certain drug overdoses, and dangerously high potassium levels that are causing heart rhythm changes. For cardiac arrest specifically, it’s no longer given routinely but is still used when the arrest is caused by high potassium, specific overdoses, or extreme acidosis.
The decision to give bicarbonate intravenously is not straightforward. In diabetic ketoacidosis, for instance, outcomes tend to be similar whether or not bicarbonate is administered, so it’s typically reserved for cases where pH stays below 7.0 after initial fluid treatment. Giving too much can overcorrect into alkalosis, which carries its own risks. Oral bicarbonate supplements, on the other hand, are a standard long-term treatment for people with chronic kidney disease whose levels have drifted below normal.