Understanding potential provocations of haemorrhage is important in a range of clinical settings, and particularly for people with abnormal vasculature. Patients with hereditary haemorrhagic telangiectasia (HHT) can report haemorrhage from nasal telangiectasia in real time, and suggested dietary factors may precipitate nosebleeds. To examine further, nosebleed severity, dietary supplement use, and blood indices were evaluated in an unselected group of 50 HHT patients recruited from a specialist UK service. Using the validated Epistaxis Severity Score, nosebleed severity ranged from 0 to 9.1 out of 10 (median 3.9). Using a Food Frequency Questionnaire, 24/50 (48%) participants reported use of dietary supplements in the previous year. A third (18/50; 36%) had used self prescribed, non-iron containing dietary supplements, ingesting between 1 and 3 different supplements each day. Eight (16%) used fish oils. Despite having more severe epistaxis (p = 0.012), the 12 iron supplement users had higher serum iron concentrations, and were able to maintain their red blood cell indices. In contrast, there was no evident benefit for the participants using non iron supplements. Furthermore, platelet counts and serum fibrinogen tended to be lower in fish oil/supplement users, and one fish oil user demonstrated reduced in vitro platelet aggregation. In conclusion, in this small study, a third of HHT patients used non-iron dietary supplements, and one in six ingested fish oils, unaware of their known anti-platelet activity. The scale of use, and potential of these "natural health supplements" to exacerbate nosebleeds has not been appreciated previously in HHT.