Credit score is affected by the amount of balance you have against the total limit. Generally, it is not recommended to have a balance of more than 35% of the total credit limit at any given point in time. However, lenders don't just look at your credit score. They pull out your whole file which shows your highest balances. If you are looking for a big loan, an evidence of borrowing more and paying on time might be to your advantage. This might be more applicable to mortgage and other stuff rather than credit cards though. Even then, use your credit card regularly. If you do so, you will be able to increase your credit limit with that credit card company.