Clinical care of patients with CF changed following COVID-19 pandemic (OGTT not performed at the CF clinic since March 2020); in consequence, this study is no longer feasible.

Cystic fibrosis (CF) patients are at risk for vitamin K deficiencies. Supplementation for fat-soluble vitamins A, D, and E is well established, but in CF, there is little data for vitamin K concerning the optimal dose and frequency of supplementation. Beyond its known role in coagulation, research has highlighted the role of vitamin K for bone health and the control of blood sugar levels. However, after pulmonary complications, the risk of diabetes and bone diseases are two important and frequent complications of CF. Patients with CF being at risk of vitamin K deficiencies, this vitamin could play a role in these complications.

The investigators propose a pilot study (carried out to assess its feasibility on a larger scale) to evaluate if a supplement of vitamin K improves vitamin K serum levels in CF patients by comparing:

• Group A: a vitamin K supplement of 2mg, every day for 6 months
• Group B: a vitamin K supplement of 7mg, twice a week for 6 months

Inclusion Criteria:

• Diagnosed with CF
• Aged above 18 years
• Pancreatic insufficient
• Subjects with an OGTT test in the last 12 months or subjects who are diabetic

Exclusion Criteria:

• Receive or have received, in the last 6 months, a supplement of vitamin K (dose greater than 500 mcg per day)
• Subjects with a pulmonary function under 30%
• Subjects with severe gastrointestinal disease (Crohn disease, coeliac disease and recent (<1 year) history of intestinal occlusion).
• Subjects with a history of liver disease (severe or transplant)
• Known allergy or intolerance to phylloquinone (oral form of vitamin K)
• Pregnancy (current or planned in the next 6 months)
• Subjects with signs of active secondary infections should wait at least 1 month after the end of antibiotic treatment in order to be included in the study.