How tall should a bedside lamp be?

The right bedside lamp lets you read without the bulb in your eyes (sample note).
Sit up in bed. The bottom of the shade should be close to your shoulder: on a standard bedside table that means a lamp of 40 to 55 cm. Lower, and the light falls on the table; higher, and you see the bulb.
Bring the height of your bedside table to the shop and we will try lamps against it.