Celtic cultural and linguistic influence did reach the Iberian Peninsula — groups like the Lusitanians and Celtiberians are well documented. But our Celtic Index is based on ancient DNA from sites associated with Continental Celtic cultures (Hallstatt, La Tène, Gaul), which are mostly from Central and Western Europe.
Ancient DNA from Celtic-associated Iberian sites is still limited in the available datasets. So a 0% Celtic Index doesn't mean there was no Celtic influence in your ancestry — it means your DNA doesn't closely match the specific ancient samples we currently use. As more Iberian Celtic samples become available, we hope to capture that regional heritage better.