You can only claim your State Pension when you have reached your State Pension age and this will depend on your date of birth.
Historically the State Pension was 60 for women and 65 for men. This started to change in April 2010 as women’s State Pension age began to increase - in stages from 60 to 65 to bring them in line with men.
Between 2018 and 2020 men’s and women’s State Pension age will increase from 65 to 66 and from 2026 to 2028 the State Pension age will rise to 67 for everyone.
The Government has announced that it will regularly review the State Pension age. The first review will be completed before May 2017.
To find out your State Pension age go to: https://www.gov.uk/check-state-pension