First u have to ensure that the oil is at the full mark. No more, no less. Try checking it early in the morning with cold engine. Take out the dipstick, wipe it off and then place it in again. Take out the dipstick again and check the oil level. It should be on the max mark. If it is not then top it up by pouring oil.
To check for reduction, drive the car about 500 kms after ensuring that thr oil is full. Then again repeat the dipstick procedure. The level should be where you had left it. If there is any reduction in the dipstick level then it means that ur car is reducing oil