The stable phase at room temperature and pressure is α-NaBH4, which is cubic and adopts an NaCl-type structure, in the Fm3m space group.

[15] In the Bayer process, it is produced from inorganic borates, including borosilicate glass[16] and borax (Na2B4O7): Magnesium is a less expensive reductant, and could in principle be used instead:[17][18] and NaBH4 reduces many organic carbonyls, depending on the conditions.

[6] These reductions proceed in two stages, formation of the alkoxide followed by hydrolysis: It also efficiently reduces acyl chlorides, anhydrides, α-hydroxylactones, thioesters, and imines at room temperature or below.

[19] Nevertheless, an alcohol, often methanol or ethanol, is generally the solvent of choice for sodium borohydride reductions of ketones and aldehydes.

The mechanism of ketone and aldehyde reduction has been scrutinized by kinetic studies, and contrary to popular depictions in textbooks, the mechanism does not involve a 4-membered transition state like alkene hydroboration,[20] or a six-membered transition state involving a molecule of the alcohol solvent.

It was suggested that the simultaneous activation of the carbonyl compound and borohydride occurs, via interaction with the alcohol and alkoxide ion, respectively, and that the reaction proceeds through an open transition state.

[9] The NaBH4-MeOH system, formed by the addition of methanol to sodium borohydride in refluxing THF, reduces esters to the corresponding alcohols.

One example is the titanocene derivative:[31] NaBH4 reacts with water and alcohols, with evolution of hydrogen gas and formation of the corresponding borate, the reaction being especially fast at low pH.

[15] Sodium borohydride has been considered as a way to store hydrogen for hydrogen-fueled vehicles, as it is safer (being stable in dry air) and more efficient on a weight basis than most other alternatives.

However, such a usage would need a cheap, relatively simple, and energy-efficient process to recycle the hydrolysis product, sodium metaborate, back to the borohydride.

[37] A common laboratory demonstration "uncooks" eggs with sodium borohydride, as hydride reagents reduce disulfides to thiols.