Credit Card Limit Decrease Can Hurt Credit Scores

Requesting a decrease in your credit limit can hurt a credit score for the same reason that closing a credit card account can.  The reason is debt utilisation ratio or balance to credit ratio.  If you’re using a certain amount on the credit limit that is available on your credit card then decreasing the credit limit will increase the debt utilisation ratio.  Meaning to say that you will be using a higher percentage of the money that is available to you on credit on that credit card.  The way to calculate a debt utilisation ratio is to add up the credit limit of your available credit cards.  Then you add the total amount of balance that you carry on all these cards combined.
For example if the credit limit of all credit cards combined is $10,000 and the total amount of balance is $5,000 then the debt utilisation ratio is 50%.  However if the limit on one of these cards were to be decreased on your request and the total credit limit of all your credit cards became $7,000 any still carried a balance of $5,000 then you debt utilisation ratio would be about 70%.
An increase in the debt utilisation ratio and result in a negative impact on your credit score as it were traced to the lender and to the credit scoring models that you are using a large amount of money as debt will, increasing the potential for default.
It may also signify that you are using credit to supplement your income owing to the responsible spending and living beyond their means.