Obtaining a certified copy of a birth certificate can take time.
If your loved one was born in the United States, then you will need to contact the state your loved one was born in to obtain the birth certificate. There may be a cost and you will need to know the city and county your loved one was born in.
If your loved one was born abroad, then you will need contact the U.S. embassy or consulate in the country of birth to obtain a birth report.
The link below is a usa.gov website that and includes links to information for each state as well as a link to Travel.State.gov for overseas births.