Extreme tiredness, high fever, hypoglycemia or low blood sugar, high blood sugar, kidney
problems causing brain fog, liver
problems causing brain fog, low electrolytes, very high blood pressure, alcohol or drug intoxication, etc can all cause slurred speech.
Apart from brain related causes like stroke, transient ischemic attack, brain tumor, bleed etc, it can also be due to sickle-cell anemia, Wilson’s disease, multiple sclerosis, myasthenia gravis or lead/mercury poisoning.