Does current matter for high/low input in circuits?
I am assuming your question is: "Does current affect the reading on microcontroller input pins?"

Typical input pins, be them digital or analog, read only voltage and are high impedance. That is to say that the input pins have a large resistance (1MΩ+), and in turn will not allow much current to flow. But there is some leakage current (often less than 1μA).

If you have a DC 5V signal and connect it to multiple input pins, you would multiply that leakage current (though the voltage would not be affected).  

However, with enough current draw, a voltage source may lower its output. Depending on the what is supplying the 5V, it is highly unlikely that the tiny amount of current would be enough to drop the voltage unless there were hundreds of input pins reading the voltage of a small capacitor that is not being charged.