Gaia brand Elderberry will show you the milligrams for the effective ingredients on the label unlike others I have seen that just claim to be strong.
If you catch yourself at first sign of illness (I take 1 tsp a day every day but you can wait till you get sick) it is best for avoiding getting totally sick.
The tiny spikes on viruses called hemagglutinin get deactivated by active ingredients in elderberries. If they can't spike the cells, then the virus is useless for getting us ill.
When I first tried this I was in the middle of a mess of a cold-loads of sneezing, coughing, and gunk making. I doubled my dose and thought I was miraculously pretty fast so I stopped. Bad choice. So if you are already sick-I believe that viral replication is in full swing, you have to stick with it longer.
I follow the label for treating my child and we haven't had to go through all the bouts of colds and flu our friends have for the last year. We used to get everyone's colds. This week we got the tiniest hint of cold coming on while someone sick exposing us at every turn of going out in public the days before and this week too. I doubled my elderberry dose and began my child's dose. She had one day of being tired after the day of slight sinus congestion! That is it!
I would love to make it myself but I do not know yet how to make it this concentrated. No one has been able yet to tell me the mg of active ingredients in their homemade brew yet.