Symptoms of beriberi include weight loss, emotional disturbances, impaired sensory perception, weakness and pain in the limbs, and periods of irregular heart rate. Edema (swelling of bodily tissues) is common. It may increase the amount of lactic acid and pyruvic acid within the blood. In advanced cases, the disease may cause high-output cardiac failure and death.

Symptoms may occur concurrently with those of Wernicke's encephalopathy, a primarily neurological thiamine-deficiency related condition.

Beriberi is divided into four categories as follows. The first three are historical and the fourth, gastrointestinal beriberi, was recognized in 2004:

- "Dry beriberi" specially affects the peripheral nervous system

- "Wet beriberi" specially affects the cardiovascular system and other bodily systems

- "Infantile beriberi" affects the babies of malnourished mothers

- "Gastrointestinal beriberi" affects the digestive system and other bodily systems

Thiamine deficiency, also known as beriberi, is a condition that occurs due to not enough thiamine (vitamin B1). There are two main types: wet beriberi, and dry beriberi. Wet beriberi results in a fast heart rate, shortness of breath, and leg swelling. Dry beriberi results in numbness of the hands and feet, confusion, trouble moving the legs, and pain. A form with loss of appetite and constipation may also occur.

Risk factors include a diet of mostly white rice, alcoholism, dialysis, chronic diarrhea, and taking high doses of diuretics. Rarely it may be due to a genetic condition which results in difficulties absorbing thiamine found in food. Wernicke encephalopathy and Korsakoff syndrome are forms of dry beriberi. Diagnosis is based on symptoms, low levels of thiamine in the urine, high blood lactate, and improvement with treatment.

Treatment is by thiamine supplementation, either by mouth or by injection. With treatment symptoms generally resolve in a couple of weeks. The disease may be prevented at the population level through the fortification of food.

Thiamine deficiency is rare in the United States. It remains relatively common in sub-Saharan Africa. Outbreaks have been seen in refugee camps. Thiamine deficiency has been described for thousands of years in Asia and become more common in the late 1800s with the increased processing of rice.