But be careful about diving right in. If you suffer from poor vagal tone, 20 minutes of stimulation twice a day will throw you into some serious healing reactions or physiological backlash. Use it like herbals or any ACM technique, test it with a very small dose, then increase slowly till you get an effect. You can monitor HRV baseline (nighttime) values (I wear an Oura ring) to watch the effects of your tcVNS grow over time. When baseline HRV oscillates, you are overdoing it, and the amplitude is proportional to the misery it will give you, nausea, diarrhea, headache, mental upset, etc.