Why do I need an 8889 form?

Since 2013 I have been on an HDHP Plan with an HSA through my employer. They contribute $800 per quarter and then I contribute variable amounts every pay period. TurboTax is now telling me that I need an 8889-T form to file my taxes, but I've never needed one before. Am I missing something? I keep reviewing my Healthcare info section and everything I've checked is accurate. Help please!