1. Avoid tea when you have a fever

The caffeine in tea can raise body temperature and reduce the effectiveness of medication.

2. People with liver disease should avoid tea

Caffeine and other substances in tea are mostly metabolized by the liver. If the liver is diseased, drinking too much tea may exceed the liver's metabolic capacity and damage liver tissue.

3. People with neurasthenia should drink tea with caution

Caffeine in tea stimulates the central nervous system. For those with neurasthenia, drinking strong tea, especially in the afternoon or evening, may cause insomnia and worsen symptoms. It is recommended to drink tea in the morning and at noon—flower tea in the morning and green tea in the afternoon—while avoiding tea at night. This helps patients stay alert during the day and calm at night, aiding sleep.

4. Pregnant women should avoid tea, especially strong tea

Tea contains large amounts of polyphenols and caffeine, which can negatively affect fetal development. To ensure normal intellectual development and avoid excessive stimulation from caffeine, pregnant women should drink little or no tea.

5. Nursing mothers should avoid strong tea

Drinking strong tea during lactation can cause excessive caffeine to enter breast milk, leading to infant excitability, reduced sleep, and frequent crying.

6. People with ulcers should drink tea with caution

Tea stimulates gastric acid secretion, which can increase irritation to ulcer sites. Drinking strong tea regularly may worsen the condition. However, those with mild ulcers can drink weak tea two hours after taking medication. Adding sugar or milk to black tea may help reduce inflammation and protect the gastric mucosa. Tea can also block the synthesis of nitrosamines in the body, potentially preventing precancerous changes.

7. Malnourished individuals should avoid tea

Tea has fat-breaking properties. For malnourished people, drinking tea may further break down fats and worsen malnutrition.

8. Drink tea with caution after intoxication

Tea stimulates the central nervous system. Drinking strong tea after intoxication can increase the burden on the heart. Tea also has a diuretic effect, causing undigested toxic aldehydes from alcohol to be excreted through the kidneys, which can irritate the kidneys and harm health. Therefore, people with heart or kidney conditions should avoid tea, especially strong tea. Healthy individuals may drink a small amount of strong tea after intoxication. To alleviate hangover, consuming large amounts of fruit or drinking small amounts of vinegar can speed up metabolism.

9. Use tea cautiously when taking medication

Different medications have different properties and interact with tea in various ways. Tannins and theophylline in tea can chemically react with certain drugs. When taking sedatives, hypnotics, iron supplements, enzyme preparations, or protein-based medications, tea polyphenols may react with iron to form precipitates, reducing drug efficacy. Some Chinese herbal medicines like ephedra, coptis, and goldthread should also not be mixed with tea. It is generally advised not to drink tea within two hours of taking medication. However, for certain vitamins, tea has no negative effect—tea polyphenols can even promote the absorption of vitamin C. Tea itself contains vitamins and has benefits such as stimulating alertness, promoting urination, lowering blood lipids, and reducing blood sugar, which can enhance drug efficacy. In folk medicine, it is also believed that tea should be avoided when taking tonics like ginseng or antler.

10. Anemic patients should avoid tea

Tannic acid in tea can bind with iron to form insoluble compounds, preventing the body from obtaining sufficient iron. Therefore, anemic patients should not drink tea.

11. People with urinary stones should avoid tea

Urinary stones are often calcium oxalate stones. Tea contains oxalic acid, which can combine with calcium excreted in urine to form stones. Drinking large amounts of tea may worsen the condition in patients with urinary stones.

12. Avoid drinking tea on an empty stomach

Drinking tea on an empty stomach can dilute gastric acid, inhibit gastric juice secretion, impair digestion, and even cause symptoms like palpitations, headache, stomach discomfort, blurred vision, and restlessness—known as "tea drunkenness." It may also affect protein absorption and cause gastric mucosal inflammation. If tea drunkenness occurs, sucking on candy or drinking sugar water can help relieve symptoms.

13. Avoid drinking large amounts of tea before and after meals

It is best not to drink tea within 20 minutes before or after meals. Doing so can dilute gastric juices, hinder digestion, and cause oxalic acid in tea to react with iron and protein in food, affecting their absorption.

14. Avoid drinking tea before bedtime

It is best not to drink tea within two hours before sleep. Tea can cause mental excitement, affect sleep, and even lead to insomnia, especially with freshly picked green tea, which is particularly stimulating.

15. Avoid drinking tea that has been left overnight

Tea should be brewed and consumed fresh. Leaving tea for too long causes loss of vitamins and other nutrients, and it may spoil or ferment, leading to illness if consumed.

16. Avoid drinking the first infusion of tea

Modern tea may be contaminated with pesticides, fertilizers, dust, and other substances during growing, processing, and packaging. The first infusion is essentially a rinse and should be poured out quickly before adding boiling water for a second infusion, which is the cleanest tea to drink.

17. Avoid drinking low-quality or spoiled tea

Tea is difficult to store properly and can easily absorb moisture and become moldy. Some people, out of frugality, may be reluctant to discard moldy tea. However, spoiled tea contains harmful substances and pathogens and should never be consumed. Even high-quality tea, if left to steep too long, can oxidize and grow microorganisms, making it unsafe to drink.

18. Children should not drink strong tea

When tea is strong, it contains high levels of polyphenols, which can bind with iron in food and hinder iron absorption, potentially leading to iron-deficiency anemia in children. Children may drink weak tea (about one-third the strength of adult tea). Preschool-aged children can drink coarser tea, which has lower polyphenol content.

19. People with coronary heart disease should drink tea with caution

For those with coronary heart disease who experience rapid heart rate, premature beats, or atrial fibrillation, caffeine and theophylline in tea are stimulants that can increase heart activity. Drinking large amounts of strong tea may accelerate the heart rate, trigger attacks, or worsen the condition. Such individuals should only drink weak tea. Conversely, those with a heart rate below 60 beats per minute may benefit from drinking more tea, as it can help increase heart rate and support drug treatment.

20. Elderly people should not drink raw tea

Raw tea refers to green tea that is dried after fixation without rolling. This tea retains a natural green color and contains compounds similar to fresh leaves, with little conversion of low-boiling-point aldehydes and alcohols. It has a strong raw, grassy aroma. For elderly people, drinking this type of green tea can strongly irritate the gastric mucosa, causing stomach pain. Even young people may experience stomach discomfort, often described as "scraping the stomach." If raw tea has been purchased, it should not be brewed directly. Instead, it can be stir-fried slowly over low heat in a non-oiled iron pan to remove the raw aroma until a slight roasted chestnut fragrance appears.

21. People with high blood pressure should avoid strong tea

Strong tea is defined as using less than 50 ml of boiling water per gram of tea leaves for the first infusion. For people with high blood pressure, drinking too much strong tea may cause blood pressure to rise due to the stimulating effects of caffeine, which is harmful to health.