They are correct that treatment can cause fatigue, as well as cancer itself, medications, any underlying medical conditions, malnutrition, dehydration, lack of sleep, being bed ridden, no exercise, age, depression, psychological, etc. It's difficult to answer what is too much fatigue, and is best answered by his doctors, and by them doing an evaluation, physical exam, blood work, and correcting any deficiencies noted, and seeing some of the above mentioned items are properly addressed if not met.

As far as nutrition, as quick guide, you basically need 12-14 calories per pound of weight to maintain it. 15-17 calories to gain, between 1 grams of protein for each pound of weight, some say twice that for healing, recovery, and half your body weight in liquids every day, but can be higher, lower based on needs, and instruction by your medical team.

I conserved energy when I could. I used a shower chair to sit on when showering, used a walker, and sat on that when cooking, which was way after treatment, and used canned nutrition solely during treatment or ordered out.

Mention your concerns to his doctor(s), and your husband's loss of mental status, which may be of concern.

Good luck with everything.