The Starvation module covers both starvation and dehydration. It is an optional system that operates similarly to what is detailed in the 1e Wilderness Survival Guide. The below are detailed in the Wilderness Survival Guide and provided merely for guidance. Likely, it will be more practical to simplify how you implement these results but that is up to each Dungeon Master to determine.
How to Use the Starvation Module
When a character(s) runs out of food and/or water, the DM should run the module. Uncheck boxes for each character missing Rations, Standard; Rations, Iron; and/or Water. Then click Calculate. The resultant table will disappear as soon as you interact with something else on the site so be sure to click the Print Table button to open a tab with a replica of this table and its data to refer to until the current malnourishment is resolved.
The resulting table will display days upon which the three phases of malnourishment occur. Namely, Weakened, Distressed, and Incapacitated.
How Results are Determined
Firstly, a character’s Tolerance Level for being without food or water is determined by calculating the combined score of both Strength and Constitution abilities. Nothing happens within this window of tolerance. When a character exceeds his tolerance level, he must make a successful check against the lower of Strength or Constitution once every 12 hours to remain unaffected by the lack of nourishment. Every check after the first one is made with a cumulative + 1 modifier on the die roll. If a character fails one of these checks, he is Weakened, and all subsequent checks are made with a cumulative + 2 modifier on the die roll. If a character fails a second check, he is Distressed, and if he fails a third check he becomes Incapacitated.
Weakened
A Weakened character suffers a -1 penalty on Attack rolls and Saving Throws related to dodging or reaction. The penalty worsens by -1 per day. The condition improves by two steps per day if at least one meal is eaten daily.
Distressed
A Distressed character continues to incur the penalties for being Weakened. In addition, he can perform strenuous activity for no more than two turns before needing to make a Constitution Check, and if he fails this check, he becomes automatically exhausted (instead of merely fatigued). If a distressed character receives nourishment and makes a successful Constitution check after the meal, he becomes Weakened and then continues to recover thereafter in the same way a Weakened character does.
Incapacitated
An Incapacitated character is, in effect, permanently Exhausted. He retains any accumulated penalties from being Weakened (or has them worsened to – 4 if they were not that low already). He is incapable of performing any voluntary physical activity, and cannot recover from his condition until and unless he takes solid nourishment for at least two consecutive days. If he eats for two days (at least two full meals, spaced one day apart) and immediately thereafter makes a successful Constitution/Strength check (whichever score is higher), he is considered Weakened and continues to recover afterward in the same way that a Weakened character does.
An Incapacitated character who does not eat within 1-2 hours of acquiring this condition will begin to lose hit points at the rate of 1d6 per hour. He takes an additional -1 penalty on attack rolls and saving throws for each hour that he loses hit points, above and beyond the penalties he had already incurred from his Weakened condition.
Fatigued
All of the ability scores of a Fatigued character, except for Comeliness, are lowered by 2. This will remain in effect until he rests for two consecutive hours.
Exhausted
An exhausted character takes an additional -2 penalty on all of his Ability scores, Attack rolls, and Saving Throws. He can attempt to defend himself or perform some other physical action when failure to move would mean risking death, but otherwise an Exhausted character is not capable of any voluntary physical activity.
