From the web....
While most LED bulbs are now dimmable, not all of them are and not all of them dim in the same manner Since LEDs consume such a low wattage, many types of dimmers do not function with LED in the same way that they do with high wattage load incandescents. When dimming an LED you may notice the following:
Smaller amount of dimming rage (Typically 70-90% range vs. 100% with incandescent)
LED Bulbs may not shut off at lowest dim setting: this is caused by the dimmer thinking the bulb is completely off due to the low amount of wattage an LED consumes.
It is suggested that you test your current dimmers to see if they work with the LED bulbs you have purchased, chances are they will likely work fine. However, if you experience any of the above issues with your current dimming control, we suggest the Lutron CL series of dimmers. These dimmers were the first to be designed with LED light bulbs in mind and offer a trim adjustment switch that will allow for full and accurate control of dimming range.