Ulnar nerve compression, carpal tunnel syndrome and peripheral neuropathy can each cause numbness of the fingers of the left hand, states the Mayo Clinic. Numbness of the fingers is rarely a sign of a life-threatening condition when it is the only symptom.
Ulnar nerve compression that occurs at the elbow, also known as cubital tunnel syndrome, causes numbness in the pinkie and ring fingers of the affected arm, notes the American Academy of Orthopaedic Surgeons. Compression of the ulnar nerve can be caused by leaning on the elbow, keeping the elbow bent for long periods of time or fluid buildup in the elbow. An irritation of the median nerve that passes through the carpal tunnel can cause carpal tunnel syndrome, which leads to numbness of the thumb, index and middle fingers of the affected hand, notes MedicineNet. Obesity, pregnancy, arthritis and repetitive work that puts pressure on the median nerve or wrist tendons can cause carpal tunnel syndrome.
Damage to the peripheral nerves that send information from the brain and spinal cord to the rest of the body can cause peripheral neuropathy, leading to numbness in the fingers, notes the Mayo Clinic. Diabetes, injuries, infections and exposure to toxins can each lead to peripheral neuropathy. When a treatable condition causes peripheral neuropathy, the numbness of the fingers may go away following treatment of that condition.