You are required to observe your vesatot from your last period. Therefore, if you are still spotting at the time you have an onah, you may be rendered niddah from the bedikah even if you are not yet actually experiencing a flow.

Alternatively, you may not notice your period until it becomes an actual flow. Even if the spotting from a few days prior is from your period and not from the Mirena, you do not have to separate until the staining becomes a flow. Usually, heavy staining can be contained by use of a single light pantyliner over the course of a day. Once the staining is heavy enough that you need a pad or a tampon, you can assume you are experiencing a flow and are rendered niddah.

Please note that even if you are not niddah from the staining, we do recommend abstaining from intercourse (but not other forms of contact) until the staining subsides.

Please feel free to get back to us with any further questions.

B'Hatzlacha!