5mg biotin daily helped heal my brittle and uneven-surface fingernails

About 2 to 3 months after I started taking "Now Foods, Biotin, 5,000 mcg, 120 Veg Capsules" (price S$12.34) daily, my fingers are much more healthy.

No more easily broken and brittle fingernails.

No more uneven surfaces on my fingernails.

I should have taken a picture of my old bad fingernails.

Note:

The U.S. Recommended Dietary Allowance (RDA) for biotin is 300 micrograms daily.

(5000 mcg)/(300 mcg)
= 16.667

It shows that a very high dose of biotin was required to heal my bad fingernails although I took lower dose of biotin before this 5000 mcg dose.

Important note: 

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Before taking Now Foods, Biotin, 5,000 mcg, 120 Veg Capsules", I took "GNC biotin 600 mcg 120 caplets" usual price S$21.50 and VIP price S$17.20. Bought in 2016 ref. R/DD2016I(ai)28. OP: dd2017C09. This 600 mcg is too low to heal my unhealthy fingernails.