Adding liquid nicotine to e liquid

[unable to retrieve full-text content]

Hey guys
Ive been having an issue with e liquid lately. Normally I vape e liquid that has 3 mg of nicotine in it, and it recently hasnt been satisfying my nicotine craving. I tried using 6 mg e liquid but its too harsh. Is there any way I can purchase liquid nicotine online and add it to my e liquid with 3 mg to make it either 4mg or 5 mg? If so, what brands do you recommend and what are the measurements?

Adding liquid nicotine to e liquid