Why do I feel sleepy after drinking coffee?

Generally, feeling drowsy after drinking coffee may be related to differences in caffeine sensitivity, increased caffeine tolerance, blood sugar fluctuations, poor sleep quality, psychological factors, and other causes. A detailed analysis is as follows:

1. Differences in caffeine sensitivity: Individuals vary in their sensitivity to caffeine. Some people may be less sensitive to caffeine, resulting in a less noticeable stimulating effect. Additionally, if the coffee concentration is low or the amount consumed is insufficient, drowsiness may still occur.

2. Increased caffeine tolerance: People who regularly consume large amounts of coffee may gradually develop tolerance to caffeine, leading to diminished alertness effects and potentially experiencing fatigue or sleepiness.

3. Blood sugar fluctuations: Caffeine can stimulate insulin secretion, which may lead to decreased blood glucose levels. When blood sugar drops too low, individuals may feel tired and drowsy.

4. Poor sleep quality: If nighttime sleep quality is poor, one may continue to feel fatigued and sleepy the next day. In such cases, drinking coffee may not fully eliminate feelings of tiredness.

5. Psychological factors: High work stress, low mood, and similar conditions can affect mental state, making it difficult for caffeine intake to effectively enhance alertness.

In daily life, it's important to develop healthy habits, avoid long-term smoking, and engage in appropriate physical exercise such as jogging or hiking, all of which contribute to overall health.