Sub-health, also called the third state is a grey period between healthy conditions and disease or unhealthy conditions.

The main syndromes for sub-health condition is manifested by bodily fatigue, difficulty in recovering after rest, body-ache, dizziness with headache, sleep disorders, lack of appetite, insomnia, lots of dreaming, palpitation, depression, anxiety, stress, fear, bad temper, and unsociable and eccentric behavior. Some serious patients suffer from low self-esteem with no desire for progress, loss of memory and concentration, and low efficiency in work and study.

According to an investigation by the World Health Organization (WHO), 70% of the world population is in Sub-health condition, where over 45 percent of sub healthy people are middle-aged or elderly.

The percentage is even higher among people who work in management positions as well as students around exam-time.