Celery seed extract comes from the seeds of celery (Apium graveolens). Its active compounds include 3-n-butylphthalide, and it is sold mainly for blood pressure.
Also known as: celery seed, Apium graveolens, 3-n-butylphthalide.
A 4-week crossover trial used four capsules a day, 1.34 g of extract in total (Shayani Rad 2022). These are study protocols, not a recommendation.
It is sold in the US as a dietary supplement. Under the 1994 dietary supplement law (DSHEA), FDA does not approve dietary supplements before they are marketed, and the maker, not FDA, is responsible for safety and labeling.
What studies show: in 52 people with high blood pressure, 4 weeks of celery seed extract on top of their usual treatment lowered 24-hour systolic pressure from about 141 to 130 mmHg and diastolic from about 92 to 84 mmHg, with no change on placebo (Shayani Rad 2022). A 2025 meta-analysis of 10 trials (511 people) found lower systolic and diastolic blood pressure, fasting blood sugar and triglycerides with celery preparations, but no effect on cholesterol, and flagged large differences between trials and small sample sizes (Liu 2025).
Safety: side effects were no more common than with placebo in both sources. People taking blood pressure medicines should ask their prescriber before adding it. The sources here do not describe drug interactions.
We could not find a single published half-life or time to peak for celery seed extract that applies to a supplement dose, so we do not list one. Plant extracts are mixtures of many compounds, so no single figure would describe them.
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