Early signs of hyperkalemia often manifest as abnormal numbness in the limbs, extreme fatigue, muscle soreness, pallor and clamminess of limbs, and in severe cases, there may be difficulties in swallowing, speaking, and breathing, and even ascending paralysis and disappearance of tendon reflexes.

The central nervous system may be affected, presenting as restlessness, fainting, and even confusion. The heart is often a major organ damaged by hyperkalemia, which can lead to a slowed heart rate. Patients may experience palpitations and panic among other discomforts, and in the most severe cases, it can cause cardiac arrest. Other symptoms may include nausea, vomiting, and abdominal pain, among other gastrointestinal symptoms.