Sage is possibly safe when taken by mouth in medicinal amounts for up to four months, such as inhaling for asthma, but it contains thujone, a poisonous chemical that can cause seizures, according to WebMD. Sage should not be used in high doses or long term.
Thujone is a potentially poisonous chemical that can damage the liver and nervous system, states WebMD. The amount of thujone in sage varies with the species of plant, growing conditions, time of harvest and other factors. Salvia officinalis is a species of sage containing high amounts of thujone. Patients with seizure disorders should not take sage in amounts higher than those typically found in food.
Ingesting sage during pregnancy is likely unsafe due to the possibility of consuming thujone, explains WebMD. Thujone can bring on a woman’s menstrual period, which could cause a miscarriage. Beast-feeding women should avoid sage due to evidence that thujone may reduce mother's milk supply. Diabetes patients may suffer lower blood sugar levels when using sage. A health care provider may need to adjust the patient's diabetes medication dosage. Scientific research has shown that sage can be taken by mouth to treat Alzheimer's disease. One gram of sage per day and a dose of sage extract, gradually increased over time to 2.5 milligrams three times daily, has been used.