What if your cortisol is a little low.

Ok I know what to do if my cortisol levels are too high but what do I do with low cortisol levels. What can I take to help with my cortisol levels should I workout hard to raise them? Is there supplements or food to help restore my cortisol levels? Whewn I workout with wieghts or do HIIT cardio I hold alot of water in my stomach for a day and then it slow goes away after one day.