Chronic Respiratory Alkalosis: This condition often results from hyperventilation, leading to a decrease in CO2 levels, which in turn causes an increase in bicarbonate to compensate. The anion gap remains normal because the increase in bicarbonate is matched by a decrease in chloride, maintaining the anion gap within the normal range.

Metabolic Alkalosis: This can be caused by various factors such as vomiting, nasogastric suction, or excessive bicarbonate intake. The body compensates by increasing CO2, but if the condition is chronic, renal compensation occurs, leading to an elevated bicarbonate level with a normal anion gap.
Compensated Respiratory Acidosis: Although less common, if a patient has a chronic respiratory acidosis (e.g., due to COPD) and is being treated or has compensated, the bicarbonate level may be elevated as a compensatory mechanism, with the anion gap remaining normal.

Milk-Alkali Syndrome: This is a condition caused by excessive intake of calcium and alkali (often in the form of antacids), leading to hypercalcemia, metabolic alkalosis, and renal impairment. It's crucial not to miss this diagnosis due to its potential for severe complications.
Severe Hypokalemia: Although hypokalemia itself does not directly cause an elevated bicarbonate, severe cases can lead to metabolic alkalosis as the body tries to conserve potassium, leading to increased bicarbonate reabsorption in the kidneys.

Licorice-Induced Metabolic Alkalosis: Certain types of licorice contain glycyrrhizin, which can cause hypokalemia and metabolic alkalosis by inhibiting the enzyme 11-beta-hydroxysteroid dehydrogenase, leading to an excess of cortisol in the kidneys.
Bartter Syndrome: A rare genetic disorder affecting the kidneys' ability to reabsorb sodium and chloride, leading to hypokalemia, metabolic alkalosis, and normal to low blood pressure. The anion gap can remain normal due to the specific nature of the electrolyte imbalances.