Heart and kidney interact

The heart and kidney balance and complement each other. The heart is in the upper burner, and belongs to fire. The kidney is in the lower burner and belongs to water. The yáng in the heart descends to the kidney to warm and nourish kidney yáng. The yīn of the kidney ascends to the heart, and nourishes heart yīn. Under normal circumstances, heart fire and kidney water interact in this way and maintain a balance. This is referred to as the heart and kidney interacting, or fire and water helping each other. Kidney yīn depletion or intense heart fire can upset this balance, causing signs such as heart vexation, fearful throbbing, and insomnia, a pattern referred to as noninteraction of the heart and kidney.