The quick method to check weather the design of slender column is fine or need to increase the column size are as follows;
1- In order to get the moments along column height accurately, divide the column into 2 or 3 segments.
2- Apply modifier.
3- Activate the P-Delta option from define menu.
4- Run the analysis and design with P-Delta and check the Non sway magnification factor i.e. delta(ns) in design summary of the column (see the pic attached). This delta(ns) must be less than 1.4. If this exceeds the limit of 1.4, increase the column size otherwise the column design is OK.
Correction by seniors in my above steps will be highly appreciated.