on one’s toes—
1. stand or walk on the front part of the feet:
- His lips fall onto my left cheek. I stand on my toes, and he hugs me tighter.
2. (coll.) active and alert; ready for action:
- We need several more salesmen who not only know the business, but are on their toes.
on tiptoe—
1. = on one’s toes 1:
- I had to stand on tiptoe in order to see over the fence.
2. (coll.) in the state of tense and eager anticipation:
- She is on tiptoe with curiosity about the present you’ve brought her.