First things first, you will have to prepare well in advance to even consider climbing Mount Whitney. What you should immediately do is get a permit. If you don't have a permit, you can not climb. To acquire one, you have to enter the Mount Whitney Lottery - Permit Reservations. Yes, you read it right, a lottery. Thousands of hikers and backpackers apply for this permit every year, but there is only a limited amount of space. The sign up for the lottery begins February 1st of each year and ends on March 15th. I will attach the link to the website for you to apply. This will tell you everything you need to know about the lottery, how it works, and your chances of getting a permit for the year you sign up.
Once you have been notified that you won reservation dates to climb Mount Whitney, you can start preparing for your climb. This means that you will have to carve out time to workout and get into serious climbing shape. If you are not one of those people who works out regularly, I would recommend 3 to 6 months of training. For me, I trained nearly every day for 3 months for this climb since I only had a short period of time after I came back from a job out of country, and, I was in decent shape to begin with. I needed to find a workout program that would get me into shape in a short period of time. I found a 12 week workout program for climbing mountains such as Whitney. It is called the 12 Week Mountaineering Fitness Plan Intermediate. This helped me and I'm sure it will help you. This will build up your endurance level and strengthen your legs for the 22 miles of hiking you will be doing. Actually if you really want to enjoy the climb, you will get there before your climb date and take one or two acclamation hikes as well, so theoretically, you will be doing more than 22 miles. I followed the exercise program pretty closely, but there were some days that I substituted exercises so that I could challenge myself more. The stair master is going to be your best friend and your worst enemy in your workouts. I would recommend doing this exercise as often as possible with a weighted back pack. I actually brought my hiking backpack to the gym and put a 35 pound plate inside. If you don't have access to a stair master, stadium stairs or walking up a steep hill is a good substitute. I have a home gym, but didn't have a stair master so I got a membership for that reason. I cannot stress enough how important it is to be in top shape for this climb. It is estimated that only a 1/3 of climbers actually make the summit due to various reasons, but mostly because they underestimated the difficulty of the climb. Altitude sickness is definitely a factor, but has nothing to do with your fitness level. Altitude sickness can affect anyone at any time. If you feel altitude sickness at any time, the only thing you can do is turn back. Altitude sickness can be dangerous and even deadly. I will talk about that a little later.
Here are examples of the first month of exercises.
All that hard work that you put into your training has to be fueled with the proper nutrition to get the results you want. I was on a strict eating diet. I meal prepped and had about 5 meals spread out during the day because I was burning so many calories from my daily workouts. I ate clean and healthy foods. For protein, I would have chicken, salmon, tuna, eggs or protein powder. For veggies, I would have pretty much anything, but my favorites were mixed veggies, brussels sprouts, green beans, or asparagus. For carbs, I would have either brown rice, oatmeal, or yams. For healthy fats, I would have avocado or nuts. I tried the best that I could to stay away from the bad foods, but I did have some cheat meals on occasion because, you know, I'm only human.