[3][5] "Lithium" is a power ballad with "cinematic production, gripping orchestration and Amy Lee's voice gliding through verses and soaring over choruses", wrote Billboard.

[7][8] Entertainment Weekly writer Jon Dolan described the song as a "tortured Queensrÿche-style pain strummer" in which Lee explores a form of addiction.

's Sam Law said it utilizes "tinkling piano", Lee's "wide-ranging vocals", and "crashes of metallic instrumentation" layered onto the composition, thematically "drawing comparisons between a medicated state and the numbness of uncertainty and depression.

[citation needed] In 2017, a reworked orchestral version of the song was recorded and included on Evanescence's fourth studio album Synthesis.

[17] Andy Gill from The Independent said it captures the album's mood "wreathed in the genre staples of black-clad, mascara'd gloom", naming it one of the standout tracks.

[20] Writing for BBC Radio 1, Fraser McAlpine felt it "seemed have lost what we liked about their singles – a bit of oomph".

[21] A Stornoway Gazette writer dubbed the song an "extreme-power-ballad maelstrom" and a "rare instance of when pop metal actually does justice to both musical genres.

"[22] IGN's Ed Thompson wrote that Lee's piano playing on songs like "Lithium" completes the album.

[24] A writer from the Leader-Post praised Lee's "stunning notes" on "Lithium", which he considered the equivalent of "My Immortal" from debut album Fallen.

[25] Writing for Revolver, Eli Enis said "Lithium" is "a prime example of Lee skillfully using her voice as an instrument that perfectly complements everything else going on around her.

"[26] Billboard regarded it as "the kind of number Evanescence was born to perform: cinematic production, gripping orchestration and Amy Lee's voice gliding through verses and soaring over choruses", concluding that Lee's "latest musical affair with darkness is captivating" and would almost make listeners "wish [their] heart was broken".

[37][38] In Ireland, the song debuted and peaked at number 30 on the Irish Singles Chart for the week ending January 11, 2007.

[39] In continental Europe, "Lithium" achieved its highest peak in Italy where it debuted at number two for the week of February 8, 2007.

[45] The clip peaked at number four on Total Request Live's countdown list of the best music videos in January 2007.

[46] A behind-the-scenes clip from the filming set of the music video was posted on January 12, 2007 on the band's official YouTube channel.