In basic medium, OH ions and water are added to balance each half-reaction. For example, in a reaction between potassium permanganate and sodium sulfite:
:Unbalanced reaction: KMnO + NaSO + HO → MnO + NaSO + KOH
:Reduction: 3 e + 2 HO +  → MnO + 4 OH
:Oxidation: 2 OH +  →  + HO + 2 e
Here, spectator ions (K, Na) were omitted from the half-reactions. By multiplying the stoichiometric coefficients so the numbers of electrons in both half reaction match:
:6 e + 4 HO + 2  → 2 MnO + 8 OH
:6 OH + 3  → 3  + 3 HO + 6 e
the balanced overall reaction is obtained:
:2 KMnO + 3 NaSO + HO → 2 MnO + 3 NaSO + 2 KOH