In Traditional Chinese medicine, the Six Levels are first heard of from Zhang Zhongjing in the Shang Han Lun from about 220 AD or about 1700 years ago.

The six stages are

• Tai Yang or Greater Yang
• Yang Ming or Bright Yang
• Shao Yang or Lesser Yang
• Tai Yin or Greater Yin
• Shao Yin or Lesser Yin
• Jue Yin or Terminal Yin

As can be seen the names of the levels are the same as the names of the head and foot pairs of acupuncture maridians. The order is rughly the order that a disease takes as you go from health to death. In some disease levels are skipped or the order can change.

Tai Yang stage is started when a person is exposed to an exterior cold pathogen. The symptoms are Fever and maybe small chills, aversion to cold, pain in the back of the neck and head, Tongue has not yet changed, Pulse is floating. This stage has two sub stages.

1. Attack by wind.

2. Attack by cold.

Shao Yang stage: fever and chills alternating, pain in the costal and hypochondriac regions, irritability, nausea, loss of appetite, bitter taste in the mouth, dry throat, blurred vision. Tongue coat getting yellowish. Pulse wiry.

Yang Ming stage