No. You're not required to deduct contributions in the year that your contributions are made. This means that contributions you make during a low-income year could be used to reduce your taxable income in a future year when you fall under a higher
tax bracket.
For example, a student who works part-time can contribute $1,000 to their FHSA but wait until they have a well-paid job after they graduate before applying the corresponding deduction. You could then get a more advantageous tax savings.