[2] On March 16, 2018, Mendes posted a collage on social media consisting of two uncaptioned images of blank color blocks after he wrote the song,[3] one in beige and one in coral.

A Rolling Stone contributor noted that the chorus features "shuddering drums" and "throbbing electric guitars", with "choral backing vocals" that "add soothing textures to the final hook".

[19] Sheet music for "In My Blood" is in the key of F major and a tempo of 70 beats per minute, while Mendes's vocals span from A3 to Bb5.

[20] Jon Caramanica from The New York Times opined it as a standout in comparison to Mendes' previous singles, referring to how "scarred and forlorn" he sounds while commending his songwriting ability.

[21] Hugh McIntyre of Forbes.com noted that the song is an evolution of Mendes' well-known sound, beginning with "a familiar acoustic guitar".

[22] Mike Nied of Idolator opined that "the sweeping anthem offers an intimate glimpse into his deepest thoughts", with a radio-friendly pop rock instrumental, adding that the song "sounds like another sure-fire smash".

Mendes became the first artist to have four number-one songs on the Billboard Adult Top 40 radio airplay chart before turning 20 years old, with "In My Blood" being his fourth.

In the United Kingdom, "In My Blood" debuted at Number 13 after one week of sales and fluctuated up and down the Top 20 before ultimately reaching its peak at 10 at the end of May.

Directed by Jay Martin, the video features Shawn Mendes lying on the floor barefoot, while his surroundings begin to change.

[citation needed] Mendes also performed the song as part of his sets on Today and at the Governors Ball Music Festival, both on June 1 in New York City,[38][39] and at Wango Tango the next day in Los Angeles.