On my online dictionary it says 気を使う also means to take into consideration. Does this mean be considerate ? Iv Heard it used in a way that it would mean that but just wanted to confirm? Thanks!
Although 使う is generally translated as "use", a more idiomatic English translation of つかう in this case would be "pay", as in "pay attention to" or "pay mind to".
Here are a couple of example sentences from スーパー大辞林, which actually uses a different kanji for つかう in this phrase: 気を遣う.
彼はまわりの人に気を遣った = He was attentive to those around him.
(私のことで)そんなに気を遣わないでください = Don't bother about me so much.