As a rule, your bedside table should sit 5-10 cm lower than the top of your...

https://amumreviews.co.uk/should-bedside-tables-be-higher-than-the-bed/

As a rule, your bedside table should sit 5-10 cm lower than the top of your mattress. This makes grabbing a glass of water or your phone effortless without reaching up or straining your shoulder