Collagen is a protein, so it won't raise blood glucose like sugars would. But I would keep an eye on the rest of the ingredients in the capsule. Sometimes they use bulking agents which may have an impact.
Having said that, how many capsules will you be taking? I imagine that it would be difficult (and expensive!) to take so many that there was a significant impact.
Also worth bearing in mind that there are a number of different types of collagen, and you need to take the right type to target the issue you are wanting to treat. Skin? joints? connective tissue? Worth doing a bit of research before you shell out £££
Hope that helps.