The four of us were going to climb the Keyhole Ridge on Longs Peak. We left the trailhead around 4:20. We made good time to the Jims Grove/East Longs Peak Trail junction arriving in exactly one hour. I checked my blood sugar level which was a bit high but nothing I was concerned about. After a quick break, we started up the Jims Grove Trail when an annoying headache I had started to intensify. Above Jims Grove, but below Granite Pass, I told Jeff I couldn't continue as I was weak, my head hurt, and I was very nauseous. As Jeff went ahead to inform Don and Brian of the situation, I puked and became very cold. When Brian and Jeff returned, I told them I'd carry out the extra gear, rest, and wait for them at the trailhead. Brian decided to go back down with me while Don and Jeff weighed their options.
I was moving slow, but felt I could get back to the trailhead. After returning to the trail junction, Brian took a break to try and enjoy at least some of the morning hike as I forged ahead. Unfortunately I didn't get far and had one of those knee-buckling, full-body, gut-wrenching spews. This one really cleaned me out. I started to feel a bit better after this, but my head still hurt and I was cold despite the moderately mild September morning. We got back to the trailhead where I rested in my vehicle. Don and Jeff had decided to come out too and arrived only minutes after Brian and I. Brian and Jeff drove me home where I slept part of the afternoon and watched some football.