There are several details to keep in mind before, during, and after decocting traditional Chinese medicine.

Before decocting herbs, select an appropriate vessel; a clay pot is ideal. Metal pots made of iron, copper, aluminum, tin, or other metals should not be used for this purpose. This is because tannins and organic acids contained in Chinese medicinal herbs can react chemically with these metals, forming precipitates that reduce the potency of the active ingredients. After each use, the decoction pot should be thoroughly washed and kept clean. For decocting, fresh, clean tap water or spring water is recommended. Water that has been repeatedly boiled or left standing in a thermos for an extended period is also unsuitable for this purpose. Herbal materials generally do not need to be rinsed, but they should be soaked in cold water at room temperature prior to decoction. Typically, herbs consisting mainly of flowers, stems, or whole plants should be soaked for 20 to 30 minutes, while those dominated by roots, rhizomes, seeds, or fruits may require soaking for 60 minutes.

When decocting herbs, the amount of water added to the herbal mixture directly affects the quality of the decoction. The traditional guideline of “three bowls of water reduced to one” is, in fact, not a scientifically sound standard. This is because different prescriptions vary in the number and potency of their ingredients, and different medicinal materials absorb varying amounts of water. Ideally, the water should cover the surface of the herbs by 2–3 centimeters (or, when gently pressing down on the herbs with your hand, the water level should just reach the back of your hand). Some herbaceous and floral medicines absorb relatively large amounts of water; if the water level drops after soaking for half an hour, additional cool water may be added to restore the proper level before beginning the decoction. The intensity of the heat used during decoction is traditionally referred to in TCM as “fire control,” which includes “gentle fire” and “strong fire.” The general principle is “strong fire first, then gentle fire”: bring the mixture to a vigorous boil over strong heat, then reduce to gentle heat and maintain a low simmer. The decoction time is calculated from the moment the mixture comes to a boil. In general, the duration of decoction depends on the nature of the herbs: for exterior-releasing herbs, the first decoction lasts 10–20 minutes and the second 10–15 minutes; for ordinary herbs, the first decoction takes 20–30 minutes and the second 15–20 minutes; and for tonifying and conditioning herbs, the first decoction lasts 30–40 minutes and the second 20–25 minutes. In addition to these guidelines, the texture of the herbs should also be taken into account: flowers, leaves, and aromatic herbs are best decocted for a shorter time, whereas mineral, bone, horn, and shell-based herbs require prolonged simmering over low heat for about an hour to ensure that their active constituents are fully extracted. As for the number of decoctions, two to three is usually sufficient. Generally speaking, after two decoctions, the concentration of active ingredients in a single dose of Chinese medicine has already decreased substantially, so two decoctions are preferable. However, for tonifying herbs and certain prescriptions with larger quantities of ingredients, a third decoction may also be appropriate.

Once the herbal decoction has been properly prepared, it should be strained and poured out while still hot; it is not advisable to leave it in the pot for an extended period. Otherwise, the medicinal liquid, which contains a high concentration of colloids, may undergo gelation as the temperature drops, making it difficult to filter, compromising the therapeutic efficacy, and increasing the risk of spoilage.

During the course of taking traditional Chinese medicine, to maximize its therapeutic efficacy, attention should be paid to certain details regarding dietary restrictions, dosing frequency, and timing, as outlined below.

After taking herbs that induce sweating to release the exterior, it is advisable to drink plenty of warm boiled water or consume warm, thin porridge. Following administration, one should lie down quietly to help the medicinal effects promote perspiration; at the same time, one should avoid sour foods and cold water.

Avoid foods that may impair spleen and stomach function and interfere with drug absorption, such as raw and cold foods, high-fat foods, sticky and greasy foods, and irritating substances.

During the course of taking traditional Chinese medicine, avoid drinking strong tea and coffee. The tannins in tea can bind with the active ingredients of the herbs to form insoluble iron tannates, thereby reducing the therapeutic efficacy of the medication.

When taking herbs that clear heat, cool the blood, detoxify and reduce swelling, calm the liver, moisten the lungs, and improve vision, one should avoid alcohol, garlic, cola, coffee, chili peppers, lamb, and other pungent, warming, and irritating foods.

When taking herbs that warm the meridians, tonify yang, astringe essence to stop diarrhea, dispel wind-dampness, and relieve cold-induced pain, one should avoid cold and cooling foods such as cold drinks, raw pears, crabs, persimmons, and bamboo shoots.

Patients with skin diseases should avoid trigger foods such as fish, mutton, stinky tofu, and pig’s head meat; patients with edema should refrain from consuming pickled foods and excessive salt.

One should avoid overdosing on medications, as this can lead to adverse consequences. An overdose of emetics may damage the spleen and stomach; an excessive dose of heat-clearing herbs can result in depletion of yang qi in the middle jiao; overuse of qi-regulating herbs readily depletes qi and harms yin; and if pathogenic factors have not yet been fully eliminated, premature use of tonifying herbs can give rise to the problem of “shutting the door and harboring the enemy.”

For common illnesses, administer one dose daily, divided into two or three servings; for critically ill patients, administer a dose every 2 to 4 hours, continuously day and night; patients with vomiting or esophageal lesions may take small doses frequently. For potent and toxic preparations, start with a low dose and gradually increase it, stopping as soon as therapeutic effect is achieved.

The timing of medication intake varies slightly depending on the therapeutic efficacy.

Morning administration: Medications that tonify yang and replenish qi, warm the middle burner and dispel cold, regulate qi and harmonize blood, and reduce swelling and disperse nodules are best taken in the morning, so as to take advantage of the body’s abundant yang and organ qi to eliminate pathogenic factors.

Take on an empty stomach: In the early morning, both the stomach and duodenum are free of food; taking medication at this time avoids interaction with food, allowing it to enter the intestines rapidly and maintain a high concentration, thereby fully exerting its therapeutic effect. Gastric tonics and anthelmintics are both best taken on an empty stomach.

Take after meals: Medications that irritate the gastrointestinal tract should be taken after meals, as the presence of food in the stomach at this time can reduce irritation to the gastric mucosa. Digestive aids and agents that promote the movement of food through the intestines should also be taken after meals.

Medicines taken before bedtime—such as those that nourish yin and strengthen the stomach, astringe essence to stop nocturnal emission, gently laxate, or calm the spirit—are best administered at dusk.

Scheduled administration: Some diseases have a predictable onset; by understanding the pattern of attack, medication can be taken appropriately in advance. For example, the formula Haoqin Wendan Tang used to treat malaria is best administered two hours before an attack.

No fixed timing for administration: Antipyretic and diaphoretic agents, as well as purgatives, should be taken in a manner that induces mild sweating or gentle laxation, without strict adherence to a specific schedule.

Menstrual-regulating medications: Should be started before the onset of menstruation.

Western and traditional Chinese medicines should be taken at least half an hour apart.