Bicarbonate is one of the most important chemical compounds in your body, acting as the primary buffer that keeps your blood pH locked within a narrow safe range of 7.35 to 7.45. It also serves as the main shuttle for carbon dioxide in your bloodstream, neutralizes stomach acid during digestion, and supports kidney function. A normal blood bicarbonate level falls between 22 and 28 mmol/L, and deviations in either direction can signal serious health problems.
How Bicarbonate Controls Blood pH
Every metabolic process in your body produces acids as byproducts. If those acids accumulated unchecked, your blood would become dangerously acidic within minutes. Bicarbonate prevents this by acting as a chemical sponge for excess hydrogen ions (the particles that make something acidic). When acid levels rise, bicarbonate binds to hydrogen ions and converts them into carbonic acid, which quickly breaks down into carbon dioxide and water. You then exhale the carbon dioxide through your lungs.
This system is called the bicarbonate buffer, and it’s the most abundant buffering system in the body. What makes it especially effective is that it’s “open,” meaning it has two exit routes. Your lungs can blow off excess carbon dioxide within seconds to minutes, and your kidneys can adjust bicarbonate levels over hours to days. At a healthy blood pH of 7.4, bicarbonate outnumbers carbonic acid by a ratio of roughly 5,000 to 1, giving the system enormous capacity to absorb sudden acid surges from exercise, illness, or diet.
Transporting Carbon Dioxide
Your cells constantly produce carbon dioxide as waste. That CO2 needs to travel through the bloodstream from your tissues back to your lungs, where you breathe it out. Bicarbonate is the primary vehicle for this trip. About 70% of carbon dioxide travels through the blood in bicarbonate form rather than as dissolved gas.
Here’s how it works: carbon dioxide enters red blood cells, where an enzyme rapidly converts it into carbonic acid. That carbonic acid immediately splits into a bicarbonate ion and a hydrogen ion. The bicarbonate then exits the red blood cell and dissolves into the liquid portion of blood, hitching a ride to the lungs. Once it arrives, the entire process reverses. Bicarbonate re-enters red blood cells, gets converted back into carbon dioxide, and diffuses into the air sacs of your lungs for exhalation. This cycle runs continuously with every breath you take.
Protecting the Digestive Tract
Your stomach produces hydrochloric acid to break down food, but the lining of your small intestine can’t tolerate that level of acidity. When partially digested food leaves the stomach and enters the duodenum (the first section of the small intestine), your pancreas releases a bicarbonate-rich fluid that can reach concentrations of up to 140 millimoles per liter. This alkaline flood rapidly neutralizes the acid, raising the pH in the intestinal space to around 8.0.
This neutralization serves two purposes. It protects the delicate intestinal lining from acid damage, and it creates the right chemical environment for digestive enzymes to work. Pancreatic enzymes that break down fats, proteins, and carbohydrates function best in a mildly alkaline environment. Without bicarbonate secretion, these enzymes would clump together in the pancreatic ducts and fail to do their job properly.
The Kidneys as Bicarbonate Managers
Your kidneys are the long-term regulators of bicarbonate in the body. They perform two critical tasks: reclaiming the bicarbonate your blood already has and manufacturing new bicarbonate to replace what gets used up neutralizing acids.
Each day, your kidneys filter a large amount of bicarbonate out of the blood, then reabsorb nearly all of it. The proximal tubules (the first filtering segment) recapture 70 to 80% of filtered bicarbonate. Another 10 to 15% gets reabsorbed further along in the filtration loop, with the remainder picked up in later segments. This reclamation process is so efficient that virtually no bicarbonate is lost in urine under normal conditions.
The kidneys also generate brand-new bicarbonate to replenish stores consumed by the body’s daily acid production. This is especially important in chronic kidney disease, where the kidneys gradually lose this ability. In a study of 134 patients with advanced kidney disease and low bicarbonate levels, those who received oral bicarbonate supplements for two years were far less likely to experience rapid disease progression (9%) compared with those who didn’t (45%). Only 6.5% of the supplemented group progressed to end-stage kidney disease, versus 33% in the control group. Separate research on over 56,000 dialysis patients found that bicarbonate levels below 22 mmol/L were associated with the highest risk of death.
Bicarbonate and Athletic Performance
During intense exercise, your muscles produce large amounts of lactic acid and hydrogen ions, which contribute to the burning sensation and fatigue that force you to slow down. Because bicarbonate buffers acid, athletes have long used sodium bicarbonate (baking soda) as a performance supplement. The International Society of Sports Nutrition recognizes it as an effective ergogenic aid for high-intensity efforts lasting between 30 seconds and 12 minutes.
The optimal single dose is 0.3 grams per kilogram of body weight, taken 60 to 180 minutes before exercise. For a 70-kilogram person, that’s about 21 grams. At this dose, improvements have been documented in cycling, running, swimming, rowing, and multiple combat sports including boxing, judo, and wrestling. Doses below 0.1 g/kg don’t produce measurable benefits, and going above 0.3 g/kg in a single dose doesn’t add further performance gains but does increase the likelihood of gastrointestinal side effects. Multi-day loading protocols using 0.4 to 0.5 g/kg per day for three to seven days before competition can also be effective.
What Happens When Levels Drop Too Low
When blood bicarbonate falls below 22 mmol/L, the condition is called metabolic acidosis. This means the body has either lost too much bicarbonate or accumulated too much acid for its buffering system to handle. Common causes include uncontrolled diabetes (where the body produces acidic byproducts called ketones), severe kidney disease, prolonged diarrhea that flushes bicarbonate out of the gut, and circulatory shock where tissues don’t receive enough oxygen and switch to acid-generating metabolism.
In these situations, medical teams may administer sodium bicarbonate directly to restore the blood’s buffering capacity. This is typically reserved for severe cases, particularly when blood pH drops below 7.0, or during cardiac arrest caused by extreme potassium elevation or certain drug overdoses.
Risks of Too Much Bicarbonate
Overconsumption of baking soda, whether for heartburn relief, detox trends, or athletic purposes, can tip the blood in the opposite direction, creating a condition called metabolic alkalosis. While baking soda overdose is considered rare, documented cases reveal a consistent pattern of complications.
The most common effects involve the nervous system. Confusion, agitation, dizziness, and loss of consciousness have all been reported. In more severe cases, patients have experienced muscle twitching, involuntary spasms in the hands and feet, seizure-like convulsions, and even coma. The heart is also vulnerable: multiple case reports describe dangerous heart rhythm disturbances, including ventricular tachycardia. One case documented hemorrhagic brain bleeding from the extreme sodium load that accompanied a baking soda overdose. Spontaneous stomach rupture has also been reported, likely from the rapid production of carbon dioxide gas when large amounts of baking soda react with stomach acid.
These cases are extreme, but they underscore that bicarbonate works best within its natural range. Your body tightly controls bicarbonate levels through the coordinated effort of your lungs and kidneys, and that regulation is one of the most fundamental processes keeping you alive.