Capacitor selection from Linear Technology generated design
It means 5 milli-ohm not mega-ohm. Imagine the capacitor part were shorted out. You'd be left with a resistor, the effective series resistor. If that we're 5 mega ohm then it's a nonsense value even for the lightest of loads on the output. Here's the equivalent circuits for capacitors, inductors and resistors. Sometimes they are shown differently but these are generally the most applicable to common circuits.







simulate this circuit &ndash; Schematic created using CircuitLab

If you are able to show the schematic, I might be able to recommend options.