Currently using the following circuit but the wheatstone resistors are 2 Mega Ohms each. I'm trying to measure the resistance of the wrist and currently struggling to pick up the small changes in the skin resistance and was wondering if there was any improvements i could make to the circuit.
You did not include your circuit
Wikipedia states;
"The voltage necessary for electrocution depends on the current through the body and the duration of the current. Ohm's law states that the current drawn depends on the resistance of the body. The resistance of human skin varies from person to person and fluctuates between different times of day. The NIOSH states "Under dry conditions, the resistance offered by the human body may be as high as 100,000 ohms. Wet or broken skin may drop the body's resistance to 1,000 ohms," adding that "high-voltage electrical energy quickly breaks down human skin, reducing the human body's resistance to 500 ohms".[15]"
So the resistance you want to measure should be between 100,000 ohms and 500 ohms.