What causes high blood pressure during the day and low blood pressure at night?

High blood pressure during the day and low blood pressure at night may be related to various factors. Common causes include physiological blood pressure variation, insomnia or sleep disorders, dosage and timing of antihypertensive medications, hyperthyroidism, and coronary atherosclerotic heart disease. Different causes require different targeted approaches. If in doubt, it is recommended to seek medical advice early and consult a professional physician. Detailed analysis is as follows:

1. Physiological Blood Pressure Variation: This refers to the normal phenomenon of blood pressure decreasing during nighttime sleep. It is a physiological response that helps the cardiovascular system rest and repair, and usually does not cause symptoms. No specific treatment is required. However, if blood pressure fluctuations are abnormal, monitoring and possible adjustment of treatment by a doctor may be necessary.

2. Insomnia or Sleep Disorders: Sleep is crucial for maintaining normal physiological blood pressure rhythms. Insomnia or sleep disturbances may lead to autonomic nervous system dysfunction, causing nocturnal hypotension, which might be accompanied by symptoms such as fatigue, difficulty concentrating, and headaches. Managing sleep habits and improving sleep quality can help stabilize blood pressure levels during both day and night.

3. Dosage and Timing of Antihypertensive Medications: If the dose of antihypertensive medication is too high or the drug's effect lasts too long into the night, it may cause excessively low nighttime blood pressure, potentially leading to symptoms like dizziness and weakness. Adjusting medication dosage or changing the time of administration—under a doctor’s guidance—is recommended.

4. Hyperthyroidism: Excessive secretion of thyroid hormones increases basal metabolism, enhances cardiac contractility, and reduces peripheral vascular resistance, resulting in lower nighttime blood pressure. This may also present with symptoms such as night sweats, anxiety, and palpitations. Thyroid function can be managed under medical supervision using medications such as methimazole tablets, propylthiouracil tablets, or carbimazole tablets.

5. Coronary Atherosclerotic Heart Disease: Thickening and hardening of blood vessel walls increase cardiac workload, leading to unstable blood pressure—such as high daytime and low nighttime readings—and symptoms including chest pain, shortness of breath, and fatigue. Treatment may include medications prescribed by a doctor, such as simvastatin dispersible tablets, atorvastatin calcium tablets, or bisoprolol fumarate tablets.

In daily life, maintaining personal hygiene and engaging in moderate exercise can enhance physical immunity and help prevent diseases.