Because of its vitamin K content, it has the potential to decrease the effectiveness of blood-thinning medications. It may increase the effectiveness is diuretics and medications that lower blood pressure. This should be watched in very elderly people who are more likely to lose their balance easily when blood pressure is too low. It has a hypoglycemic effect of its own. Nettles may still be used in any of these conditions, but a consistent daily amount should be taken to allow for adjustments in medications if necessary.
Stinging nettle is truly a useful herb even if it is a pain to pick.
It is one of the best sources of minerals and has a wide variety of uses. It may even be considered a food when picked in the spring. Of course, don't forget your gloves. IBIS Interactions, Integrative Medical Arts, 1999.