Untreated, beriberi is often deadly. With treatment, symptoms usually improve quickly.
Heart damage is usually reversible, and a full recovery is expected. However, if acute heart failure has already occurred, the outlook is poor.
Nervous system damage is also reversible, if caught early. If it is not caught early, some symptoms (such as memory loss) may remain even with treatment.
If a patient with Wernicke's encephalopathy receives thiamine replacement, language problems, unusual eye movements, and walking difficulties may go away. However, Korsakoff syndrome (or Korsakoff psychosis) tends to develop as Wernicke's symptoms go away.