Ammonia sickness refers to the toxic effects of ammonia building up in your body, most commonly in the bloodstream. The medical term is hyperammonemia, and in about 90% of adult cases, it stems from advanced liver disease. Your liver normally converts ammonia, a waste product of protein digestion, into a harmless substance called urea that leaves through your urine. When this process breaks down, ammonia accumulates and poisons the brain, causing symptoms that range from mild confusion to coma.
Ammonia sickness can also refer to breathing in ammonia gas, a separate but related concern for people who work around industrial chemicals or cleaning products. Both forms are serious and worth understanding.
How Ammonia Damages the Brain
Ammonia freely crosses from the blood into the brain. Once there, specialized brain cells called astrocytes try to neutralize it by converting it into a compound called glutamine. The problem is that glutamine pulls water into those cells, causing them to swell. This swelling creates pressure inside the skull. In severe cases, it can progress rapidly to dangerous brain herniation, where brain tissue is physically displaced by the pressure.
This process explains why ammonia sickness is primarily a neurological problem. Even though the root cause is often in the liver or gut, the symptoms you experience are almost entirely related to brain function.
What Causes Ammonia to Build Up
Liver Disease
Cirrhosis is the most common cause. Whether from chronic hepatitis B or C, alcohol-related damage, or rarer conditions like Wilson disease, a scarred liver gradually loses its ability to process ammonia. Acute liver failure from viral infections, toxins, or reduced blood flow can also trigger a sudden spike. In some people, blood vessels reroute around the liver entirely (called portosystemic shunting), meaning ammonia-rich blood from the gut never gets filtered at all.
Genetic Conditions
Some people are born with partial defects in the urea cycle, the chemical pathway the liver uses to convert ammonia to urea. These defects involve missing or underperforming enzymes. One of the most common is ornithine transcarbamylase deficiency, which is inherited through the X chromosome. Partial defects can go undetected for decades, only surfacing during periods of physical stress. Known triggers include heavy exercise, high-protein meals, pregnancy and childbirth, surgery, febrile illness, military training in young men, and certain medications like valproate (a seizure drug).
Other Causes Without Liver Disease
Several conditions can raise ammonia levels even when the liver is healthy:
- Certain infections: Bacteria that produce an enzyme called urease (including Proteus, Klebsiella, and some Staphylococcus species) can generate ammonia directly, particularly during urinary tract infections with obstruction.
- Medications: Valproate is the most well-known offender, especially at high doses or when combined with topiramate. Certain chemotherapy drugs can also cause temporary ammonia elevation.
- Kidney failure, severe dehydration, or gastrointestinal bleeding: Each of these overwhelms the body’s ability to clear ammonia through its normal routes.
- Blood cancers: Leukemia and myeloma can produce ammonia through high cell turnover.
Symptoms by Severity
Ammonia sickness typically progresses through recognizable stages. Early on, you might notice subtle personality changes, shortened attention span, or difficulty sleeping. These symptoms are easy to dismiss or attribute to fatigue.
As ammonia levels climb, confusion becomes more obvious. Speech may become slurred, reaction times slow, and disorientation sets in. A characteristic sign at this stage is a distinctive hand tremor: if you extend your arms and flex your wrists back, your hands will flap involuntarily, almost like a bird’s wings. Doctors call this asterixis, and it is one of the hallmarks of ammonia-related brain dysfunction.
In the most severe phase, a person may become unresponsive or slip into a coma. Brain swelling at this point becomes life-threatening and requires emergency treatment.
Normal Ammonia Levels and Diagnosis
A normal blood ammonia level for adults falls between 10 and 80 mcg/dL (or 6 to 47 μmol/L). Newborns naturally run much higher, at 90 to 150 mcg/dL, because their livers are still maturing. The blood test is straightforward, but the sample needs to be handled carefully and processed quickly, since ammonia levels can rise artificially if the blood sits at room temperature.
Doctors typically order the test when someone with known liver disease shows neurological changes, or when an otherwise healthy person develops unexplained confusion. Additional testing may look for liver function, kidney function, or genetic markers of urea cycle disorders depending on the suspected cause.
How Ammonia Sickness Is Treated
The first-line treatment for ammonia buildup related to liver disease is lactulose, a synthetic sugar that works in two ways. Bacteria in the colon ferment it into acids, which lowers the colon’s pH and makes it harder for ammonia to be absorbed into the bloodstream. It also acts as an osmotic laxative, physically flushing ammonia-producing bacteria and their byproducts out of the gut more quickly.
For people who don’t respond well to lactulose alone, or who have recurring episodes, a gut-targeted antibiotic called rifaximin is often added. It stays mostly in the intestines rather than being absorbed into the bloodstream, and it works by reducing the population of ammonia-producing bacteria. A combination of both treatments is more effective than either one alone for preventing repeat episodes.
For genetic urea cycle defects, treatment focuses on avoiding known triggers and sometimes using specialized medications that offer the body alternative chemical routes to eliminate nitrogen waste.
Diet and Long-Term Management
One of the most persistent myths about ammonia sickness is that you should eat less protein. Current guidelines from the American College of Gastroenterology actually recommend against protein restriction, even in people with active symptoms. Studies show that cutting protein below 0.6 grams per kilogram of body weight worsens muscle loss and nitrogen balance without improving brain symptoms. Reintroducing protein at 1.2 grams per kilogram actually improved cognition in those same studies.
The type of protein matters more than the amount. Plant-based protein sources are preferred because they contain higher levels of arginine and fiber, both of which help the body process ammonia more efficiently. In a trial of 120 patients, those eating vegetable protein saw improvement in subtle cognitive symptoms 71% of the time, compared to 23% for those on other protein sources. Their risk of a full encephalopathy episode also dropped roughly in half.
Branched-chain amino acid supplements, often sold as BCAAs, have strong evidence behind them for people with liver-related ammonia problems. Muscles use BCAAs to help clear ammonia from the blood, and people with cirrhosis are often deficient in them. A large review of 16 clinical trials found that oral BCAA supplements improved encephalopathy symptoms and, when analyzed more strictly, reduced mortality by about 24%.
A late-evening snack of around 700 calories is also recommended. Going overnight without eating triggers the body to break down its own muscle for energy, which releases ammonia. A bedtime snack reduces this protein breakdown, improves nitrogen balance, and lowers the risk of complications including fluid buildup and encephalopathy episodes.
Ammonia Gas Exposure
Ammonia sickness can also come from breathing ammonia fumes, a concern in agricultural settings, refrigeration plants, and anywhere concentrated cleaning products are used. OSHA sets the workplace exposure limit at 50 parts per million (ppm) averaged over an eight-hour shift, while NIOSH recommends a stricter limit of 25 ppm. Concentrations of 300 ppm are considered immediately dangerous to life.
At lower concentrations, ammonia gas irritates the eyes, nose, and throat. As exposure increases, it causes breathing difficulty, wheezing, and chest tightness. High-level exposure can trigger pulmonary edema, where fluid fills the lungs, producing pink, frothy sputum. Liquid ammonia, which is used in industrial refrigeration, causes chemical burns on contact and can produce frostbite because it evaporates at extremely low temperatures. Unlike the metabolic form of ammonia sickness, gas exposure is treated by removing the person from the source and supporting their breathing, rather than targeting gut ammonia production.