He should definitely have his vitamin D and Vitamin B12 checked.  I have celiac and i always felt tired, sometimes i described it as dopy.My vitamin D is always low at times extremely low which can affect you. But  I also did some research and contacted my doctor to see if she checked my Vitamin B12 and She said she didn’t check my vitamin B-12 because a wasn’t Anemic and the normal protocol is , if you are not Anemic they don’t test for B-12.  She had no problem doing the test for me and it came back super super deficient . So I was given a shot of B12 once a week for 4 weeks and I give myself 1 shot intramuscular once a month now for 18 years. Once your B12 is low it can take a long time to bring it back up and sustain it. I think it took about 6 months to get a decent number and about a year to get it right. I do get my Vitamin D checked but not yearly more like every other year because it is a more expensive test and I tend to always be low. I do take a vitamin D supplement but I would talk to your doctor before taking a supplement to make sure you don’t take too much especially if you are already taking a multivitamin. Because too much D can also have some bad side effects.  Celiacs tend to be able to take a higher dose due to our digestive and malabsorption issues but always talk to your doctor before taking. Other things could be making him feel extremely tired  like new allergies like pollens, animals, molds etc.. sleep apnea is a huge one( cause extreme fatigue) and some medications. Just other things he can have checked! Good luckÂ
