the allowed concentration differers based on what type of product you are making- from 5% in shower gels to 100% in make-up removers; what are you making? that would be a simple answer - there are other things to consider, like type of dosage form/other ingredients/how often used to assess the safety.
also, check the purity of your D5- D4 is toxic to reproduction and prohibited in cosmetics in EU.
also, keep in mind that D5 will be reevaluated in the near future and some things may change.
happy formulating !