Baldur’s Gate 3 spells stopped working? Check slots and concentration

An empty spell slot and a broken concentration spell are different problems. A slot is a resource spent to cast; concentration maintains certain ongoing effects. If a spell has ended, check which one occurred before spending another slot.

This guide covers the base game without assuming mods. Spell availability, resources and recovery depend on the character's class and abilities; inspect that character's tooltips rather than assuming every caster follows the same rest rule.

The button is unavailable: check the slot first

Select the character and inspect the spell description and available resources. A levelled spell usually needs an appropriate spell slot, though abilities, items and other exceptions can change the cost. Cantrips and spells are distinct; read the selected ability rather than assuming every cast uses a slot.

If the required slot is exhausted, use another available action or cantrip and plan a rest when appropriate. Many ordinary spell slots recover on a long rest; Warlock pact slots have different recovery rules. Check the character's resource description, supplies and current quest circumstances before resting. Resting is not a universal way to avoid time-sensitive consequences.

The effect ended: check concentration

Inspect the spell tooltip for the concentration tag. A character can maintain only one concentration spell at a time. Casting another concentration spell breaks the previous one; a spell without that requirement does not replace it merely because it is another spell.

Damage can also interrupt concentration. After taking damage, the caster makes a Constitution saving throw; failure ends the effect. The difficulty is 10 or half the damage taken, whichever is higher. Certain conditions, including being downed, can also end concentration without that damage save. If the effect disappears, check recent damage and conditions as well as the next spell you selected.

Practice with a simple fight

Suppose your caster has an active concentration spell protecting an ally and still has a suitable spell slot. Before choosing a second spell, read its tooltip:

1. If the second spell also requires concentration, decide whether replacing the protection is worth it. Casting it ends the first concentration effect.
2. If it does not require concentration and its other requirements are met, it does not break the first effect simply because you cast a spell. The caster can still lose concentration later from damage or a condition.
3. If the caster is hit and the effect disappears, check the combat log for the saving throw and the character's condition. Reposition behind allies or away from the next threat before deciding whether to spend another slot.

Do not promise that standing farther away guarantees concentration: ranged attacks and area effects can still hit. The useful habit is to reduce unnecessary exposure and check the active effect before replacing it.

Sources: bg3.wiki: concentration · bg3.wiki: spells and spell slots · Spike Chunsoft official combat guide