Usually, you can test about 3 to 4 days after you suspect implantation bleeding, but waiting for your missed period is always safest. Testing too early might just give a false negative and cause unnecessary stress.
I'd say wait at least 4-5 days so you don't waste money on multiple kits. Treat yourself to some nice street food or dessert to distract yourself while you wait!
Honestly, trying to wait is the hardest part! But testing immediately after implantation won't show anything because the hormone needs time to build up. Give it at least 4 days, or you'll be squinting at blank sticks like I did!
Don't rush to test the very next day, it won't show anything. Wait for at least 4-5 days after implantation, or better yet, wait till your period date. Keep some patience, it helps.
I would suggest waiting until your period is actually missed to get a reliable result. If you are experiencing unusual cramping or spotting, it is always better to consult your doctor instead of guessing with home tests.