The FloodReady Website is a network of stream gauges across Lycoming County which helps residents track the water levels in our creeks and river, current rain fall information, and history of flooding at various gauges. This site gives near real time readings and helps residents prepare in the event of flooding.
The half life of doxy is 18-22 h. Since you took four days' worth, you were in steady state. In five half lives 95% of the drug would be eliminated, and in 7 half lives, 99% is eliminated.
In other words, taking how much time Doxycycline will remain in your body is the best parameter for all tissue, all organisms unless your mention. 5.5 x elimination half life in hours is the time for full removal from the body. Take it as 5.5 x 22 hours = 121 hours = 5 days.