erratic oil pressure can be a sign the pump is sucking air because of low oil in the sump, also if the pressure is low, it could be that the oil is hot because there is less of it to dissipate heat, another function of oil besides lubrication.

Does the pressure gauge directly indicate low level... no, but it will give hints if you read it right.

 

If you suspect you are losing oil, check it often. Any indication of low oil level on pressure guage and it will be too late.