I dont know where you are so I dont know what meters you have to choose from. In the USA all meters have to be 80% accurate.
I take my meter to the MD and when they do a blood test I do too I try to use the same blood drop.
Some meters are more accurate than others. Some perform better than the minimum required range of 20%. I also compare my meter with my doctors from time to time. For some meters, the manufacturer may offer a standard solution so you can test the accuracy of your meter.
Some meters come with a control solution or a control solution can be ordered for some meters. I personally know that the Freestyle Lite and Bayer Contour Next have a control solution for calibration. You would probably need to ask your Pharmacist about ordering the solution. Another reason why you might be strange readings is that the battery in the meter needs to be changed. I would recommend that you keep extra batteries on hand for your meter and change the battery every 6 months.
Good luck and I hope this helps.