How to Increase Serotonin Levels Naturally. Part of the series: Natural At-Home Remedies. Exercise, Vitamin D, and St. John's Wort are all excellent ways to increase serotonin levels. Learn how to incorporate these methods into your daily life with the helpful tips provided by an expert herbalist in this free video on how to increase serotonin levels naturally. Read more: http://www.ehow.com/video_7489640_inc...