This research took a social constructionist stance and explored how Borderline Personality Disorder (BPD) is constructed by Twitter users who identify with this diagnostic label. Consistent with this position, a critical discourse analysis (CDA) methodology was employed. The data comprised two-hundred and twenty-five tweets. Tweets from professionals, or links to blogs, were excluded, in an attempt to ensure only personal tweets were used. Two interpretative repertoires were produced from the analysis: BPD as an existence of tension and BPD as a different existence. The findings indicated that authors were involved in a negotiation between themselves and BPD, which had an impact upon their felt sense of agency/control over BPD. Likewise, authors constructed themselves in opposition to individuals who did not identify with the diagnosis of BPD. Whilst this provided more favourable positions, it potentially limited access to healthcare professionals and services. The research highlights the importance of the terminology and language clinicians employ when working with clients and other professionals, as they may inadvertently disempower or stigmatise. As CDA does not assume equivalence between individuals' accounts and their internal experiences, future research may need to explore the experience of stigmatisation through social networking sites.