Reading Menta Sturgeon's account of Russell's last days, it sounds like Russell had worsening cystitis and thus avoided food and drink, and experienced severe dehydration and starvation while pushing himself past the point of exhaustion with insomnia.
October 16: "He often told us of late that he scarcely slept at all, was awake every hour of the night, and thought pretty much day and night...He always ate sparingly and would carefully note the effect of everything he ate and drank. Frequently would he divide his portion with his companion".
October 18: "There was no dining car on the train, and neither could we secure anything to eat on account of uncertainties. It was at this point that a box of peanut butter sandwiches, which had been given to us by a thoughtful friend in Brooklyn, came in just right. It made our breakfast, and afterwards our lunch". "All of this occurred after a few hours' rest during the previous night and with but little to eat".
October 22: "Boarding the train at Dallas that night, October 22d, Brother Russell was tired, and his head was aching. Some medicine was taken, and he retired".
October 23: "Upon arriving in Galveston the next morning, he was not well by any means....There were nine brethren who took dinner with us that day at the Hotel Galvez; and he answered their questions,and seemed to enjoy the fellowship and the meal. This proved to be the last meal that Brother Russell ate. Hereafter it was to be a little fruit juice, a swallow or two of a soft-boiled egg, or something like that." (So for eight days thereafter, Russell did not eat an actual meal)
October 24: "Travelling all night and reaching the home of Sister Frost Tuesday morning, it was not surprising to find him in much physical pain. His labors were telling on him more than ever. His overworked body began to break at its weakest point. Cystitis was becoming acute....He appreciated the kind offer [to see a doctor], but indicated that he would not need a physician's services....The choicest of fruit was placed just outside his door, but he did not touch it." "He went to dinner with us, talked pleasantly to everyone, and was as humorous as usual; but he ate nothing, although the dinner was excellent."
October 25: "The next morning he was a sick man, although he was not ready to admit it. He kept to his bed all day Wednesday. While he lay there in his berth, I took a seat on the couch, near him. I watched every move he made, stroked his head, and thought what a stupendous amount of work that brain had done. Taking his soft, gentle right hand and letting it rest in the palm of my left hand, I gently stroked it with my right...We then talked about his physical condition...Every move he made and every word he uttered only made me think the deeper, and yet I could hardly think of Brother Russell's life coming to a close...I answered his question by saying, 'Since we have done everything we know, and you are getting weaker all the time--your vitality is being drained while you are eating nothing to replenish it--I think that if we return to Brooklyn, you will find something there that will put you on your feet again' ".
October 26: "It was difficult to give him a drink of water without spilling it except we first raised him."
October 29: "Our train was an hour or more late in arriving in Los Angeles on Sunday morning, October 29th, and we had had nothing to eat. The brethren were rejoied to see us, but their countenances changed when they saw our dear Brother Russell. They saw that he was weak, but they knew not how sick he was. Besides, he would not yet admit that he was really sick. By ten o'clock we had reached the hotel, and I asked him if I could nto get him something to eat. He said he was not hungry and asked me to suggest something. This I did. He consented to my getting something, but only tasted a little of it. Upon bringing it to him, he asked if I had had my breakfast; and when I answered, no, he wanted to know why. I told him that it was becuase I wanted him to have his first. He said he would nto eat his until I had first had my breakfast."