What is the meaning of UID?

Answer 1

You mean IUD. It stands for Intra-Uterine Device and is often called the coil. It's a form of Birth Control invented about 2,000 years ago by the Arabs. It normally consists of a piece of plastic and copper inserted into the uterus. Another variation is the Mirena coil, which contains Levonorgestrol in a plastic tube, which is released into the uterus and is the most reliable form of contraceptive currently available. Sometimes the Mirena coil is called the IUS, which stands for Intra-Uterine System. It lasts for about 5 years.

All IUDs should be inserted under proper local anaesthetic (in the form of injections into your cervix at the 4 o'clock and 8 o'clock positions) like the injections that you have for dental treatment. It the doctor or nurse offers you only lidocaine gel, go elsewhere for your birth control as it doesn't work and they'll end up scraping you off the ceiling.

Alternately, if you meant UID as you wrote, this is a dosage frequency meaning once a day (uni in die), although it is more commonly written as QD or qd.