There are several route choices and each one has options regarding the duration. Adding an acclimatization day helps immensely in achieving your goal. The shortest standard itinerary is 5 days but that is not recommended and has the lowest success rate. The longest standard itinerary is 9 days. 6 - 8 days are the most common. Marangu route is different than the others in that it has overnights in dormitory style huts with solar power. All other routes are camping routes.
Mt Meru is Kilimanjaro's little sister. Located in nearby Arusha Nationa Park, it is the second highest mountain in Tanzania. It is much less climbed but often used as an acclimmatization climb before attempting Kilimanjaro. But Mt Meru is a great climb in its own right. Meru is a great preparation hike for climbing Kilimanjaro, or a spectacular trek for those not compelled to do Kilimanjaro. You will hike past wildlife and on the summit, witness the towering Mt. Kilimanjaro on the horizon. While typically done in only 4 days, it is not an easy peak to summit.
To reach the top, there is some scrambling on rocks in the dark and at high altitude. You should be prepared for at least 10 hours of hiking on summit day. For an easier hike, you can climb just to Rhino Point for sunrise, and then descend (just ask us.) Mt. Meru is in Arusha National Park. The park requires all groups to be accompanied by a park ranger. This ranger is employed directly by the national park. He will carry a rifle, which is available to scare away any advancing animals such as elephant or cape buffalo. You will also have your own guide, who is managing the crew and watching out for your safety. There is only one route and overnights in dormitory style huts are the only option for this climb.
**Also available as a Day Trip excursion.