Lenders and others usually use your credit report along with additional finance factors to make decisions about the risks they face in lending to you. Having negative information on your credit report or a low credit score could suggest to lenders that you are less likely to pay back your debt as agreed. As a result, they may deny you a loan or charge you higher rates and fees.
Credit scoring models usually take into account how much you owe compared to how much credit you have available, called your credit utilization rate or your balance-to-limit ratio. Basically it's the sum of all of your revolving debt (such as your credit card balances) divided by the total credit that is available to you (or the total of all your credit limits).