If you're entitled to Carer's Allowance and haven't reached State Pension age yet, National Insurance contributions are credited automatically to increase your future entitlement to the State Pension, unless you've kept the right to pay married woman’s reduced-rate contributions.
If you're under State Pension age and you become sick, you may qualify for ‘new style' Employment and Support Allowance (ESA) based on National Insurance credits from when you received Carer's Allowance.
An exception applies to carers, provided you have claimed Carer's Allowance for just 1 week in the last complete tax year before the year that you claim ESA. This type of ESA is not means tested.