Before meals on an empty stomach (the classical text specifies 食前温服, 'warm administration before eating'), typically 30 minutes before meals, once or twice daily.

Short-term use: typically 1–2 weeks for acute Dampness patterns. Should be reassessed promptly and discontinued once symptoms resolve, as the drying nature can injure fluids with prolonged use.

While taking Ping Wei San, avoid cold and raw foods (salads, iced drinks, raw fruits in excess, sashimi), as these contribute to Dampness and Cold in the Spleen and Stomach, directly opposing the formula's purpose. Greasy, fried, and heavy foods should also be limited since they generate more Dampness. Dairy products, especially cold dairy like ice cream and yogurt, tend to be Dampness-producing and should be minimized. Excessive sweets and sugar-laden foods should be reduced, as sweetness in excess can clog the Spleen. Favored foods include warm, lightly cooked meals: congee (rice porridge), soups, steamed vegetables, and modest amounts of aromatic spices like ginger, cardamom, or dried tangerine peel that support digestion. Small, regular meals are preferable to large, heavy ones. The classical administration method — taking the formula on an empty stomach with ginger and jujube dates — reflects the principle of allowing the herbs to reach the Stomach without interference from food.

Ping Wei San is classified as a Dampness-expelling formula and is known for its functions of drying Dampness, strengthening the Spleen, promoting the flow of Qi, and harmonizing the Stomach. It is primarily used to treat patterns of Dampness Stagnating in the Spleen and Stomach.
Symptoms it addresses include distension and fullness in the epigastrium and abdomen, lack of appetite, a bland taste in the mouth, nausea and vomiting, belching with acid regurgitation, a heavy sensation in the limbs, lethargy, and a tendency towards loose stools. The tongue typically has a thick, white, greasy coating, and the pulse is moderate.

Clinically, Ping Wei San is often used to treat chronic gastritis, digestive disorders, and peptic ulcers, particularly when these conditions are associated with Dampness obstructing the Spleen and Stomach.

Gan Cao (Glycyrrhiza / Licorice): Gan Cao contains glycyrrhizin, which can cause pseudoaldosteronism (sodium retention, potassium loss, elevated blood pressure) with prolonged use. It may interact with antihypertensive medications (reducing their effectiveness), diuretics (especially thiazides and loop diuretics, increasing potassium depletion risk), corticosteroids (compounding fluid retention and adrenal effects), and cardiac glycosides such as digoxin (hypokalemia from licorice potentiates digoxin toxicity). Patients on warfarin or other anticoagulants should also be monitored, as licorice may affect drug metabolism.

Hou Po (Magnolia bark): Contains magnolol and honokiol, which have demonstrated GABAergic and mild sedative activity in pharmacological studies. Caution is warranted if combined with benzodiazepines, barbiturates, or other CNS depressants, as additive sedation is theoretically possible.

General consideration: The formula's overall warm, drying nature may theoretically affect the absorption or metabolism of concurrently taken medications by influencing gastrointestinal motility and fluid balance. Patients taking multiple pharmaceutical medications should consult both their prescribing physician and a qualified TCM practitioner before combining this formula with drugs.