There are many reasons for vertigo when patients are lying down, and they need to be investigated by a doctor, including otoliths, hypoglycemia or hypotension, anemia, etc. 1. otoliths: benign paroxysmal positional vertigo, in which the otoliths are dislodged due to trauma, metabolic abnormalities, etc. The common symptom is transient vertigo, which occurs when there is a big change in the position of the head, such as when waking up in the morning or turning over on the side to lie down; 2. hypoglycemia or hypotension or hypotension: Patients with low blood pressure or hypoglycemia may have vertigo when lying down, and the vertigo is usually more obvious after the body is upright; 3, anemia: Elderly people, weak and anemic people may have vertigo when lying down if they do not pay attention to daily living and diet, so that the body has insufficient blood supply; 4, other reasons: pregnant women in late pregnancy may have vertigo when lying down because the enlarged uterus compresses the inferior vena cava and affects blood return flow, which may easily lead to vertigo.