Concatinated If Statements when a value is between 2 numbers

I hope someone can help me with this problem:

I am evaluating a field on each line of a spreadsheet

for each field evaluated I want the following:

Upper Bound Lower Bound Return this text
5 3.51 High
3.5 2.1 Medium
2 0 Low

If the field is blank, return something that tells me that.

So for example if the number evaluated is 2.7, I would expect the field to be populated with "Medium"

Please help.

Thanks,
Anne