I am a huge fan of the triple Boron complex(this triple complex has very high bioavailably other forms much less)at 6mg per day empty stomach there were increases in lebido suggesting a free testosterone increase. My bound and free testosterone has been tested as low in the past.
There are multiple NIH studies with 12mg Boron used per day and have shown increases in testosterone, vitamin D and decreases in inflammation markers in as little as 7 days.
At 15mg per day there were huge increases in lebido and mild decreases in Candida symptoms(which was my attempt).
However being at the 15mg dosage for around two months and thanks to this post I know that I have developed Vitamin B2 deficiency symptoms.
-My lips are so incredibly cracked and actually bleed, have mild light sensitivity, blood shot eyes and slightly blury vison at times.
I take Hydroxocobalamin (although very little of late) 50mg P5P, 10mg Biotin(for Candida) daily. No other B vitamins.
So yes will be adding a B2 supplement soon and monitor things from there.
EDIT:
I believe the "Life Extension Boron" add B2 to there Boron supplements for a VERY good reason.
https://www.ncbi.nlm.nih.gov/pubmed/21129941