Is day after missed period too early to test?

No: Home pregnancy tests can show positive as early as 3-4 days after implantation. Implantation generally occurs 6-12 days after ovulation. So if the egg was fertilized right at ovulation and you used the most sensitive home test it could be positive at 9 days. On average it is 13-14 days after fertilization/ovulation when it is positive. Best results are 5-6 days after kissed period.

No: go for it. Can repeat in a week if negative and still no period.