Looking for a bit of help here. I have a mid-2009 MacBook Pro that I'm having an issue with; essentially, my memory is always very low despite having almost no applications open. Here are my specs:
Processor: 2.53 GHz Intel Core 2 Duo
Memory: 8 GB 1067 MHz DDR3 **** (note: my MacBook Pro was purchased with 4 GB of memory but since I started having this problem, I purchased two 4GB memory sticks online, ie. 8GB total, and installed it myself - this problem has been happening since before I installed the new parts).
Storage: 500 GB SATA disk (211.72 GB free) **** (note: my original hard-drive crashed a little over a year ago so I had a new one installed through an apple certified repair center.. don't know if this could be causing the issue?)
Right now, I have Safari, iTunes and Microsoft Word open and I have 80.78 mb of memory free (I am constantly running the app Memory Clean).
If you're running Mavericks, then what you describe is normal. All or almost all memory is usually active. That's what you would want, since if the memory is not being used, it's being wasted.
In Activity Monitor, select the Memory tab and look at the MEMORY PRESSURE graph. If it's in the green zone, you don't have a problem.
No matter what version of OS X you have, applications such as as "Memory Clean" are counterproductive and shouldn't be used.