I would look for a different cause.
First- make sure you're using the test kit right, especially if its API. Give it a good shake.
Possible causes: over feeding, plant decay, DIRTY FILTERS and others
I caps that because I found that to be the root cause of my extremely high nitrates at the time. I did a rinse of biomedia (in removed tank water) and changed out my disposable media (filter floss) and that solved the problem.