We summited the mountain with the company Huayna Potosi Refugios, I wouldn't go with any other company.
We got the 3 day option with a sleeping bag for 1,000Bs.
They have better food, all equipment was fine and have their own private lodge 200m higher than all other companies so you will have less to walk on the last night, making it easier to summit.
They say they have an 80% success rate, we had a group of 9 and 2 didn't make it.
My two tips to help summit are:
take a sugary drink like Powerade or soft drink for energy, everyone says bring chocolate but we did and it just basically froze in our bags and we didn't stomache it, we had a small energy drink and it was so much better but had to savor it.
We met a couple that couldn't summit because it was getting too late and the sun was coming out, so the earlier you leave the refugio the more you can take your time and make it to the summit before the sun comes out.
If the sun comes out and you haven't made it, the guide will make you turn around even if you feel fine.
We left at 1AM and were the second group to summit, some leave at 2AM and don't have enough time to summit, but depends how fast you are.
It was the hardest thing I've ever done but probably the highlight of a 7 month trip.
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