Taking 10 grams of L-citrulline daily for four weeks leads to a measurable improvement in blood vessel function and a small reduction in blood pressure in women with high blood pressure who have gone through menopause.

Taking 10 grams of L-citrulline daily for four weeks lowers aortic systolic blood pressure by 4 mmHg in postmenopausal women with hypertension, without altering aortic stiffness, suggesting a direct effect on blood vessel tone.

Taking a specific amino acid supplement (L-citrulline) twice a day for a week doesn’t make blood vessels open up better in healthy people with a certain chemical imbalance, even though it raises some markers linked to blood vessel health—so short-term use probably won’t help their circulation.

Taking 10 grams of L-citrulline daily for four weeks increases blood flow and vessel dilation in the forearms of hypertensive postmenopausal women during handgrip exercise.

Taking at least 6 grams of L-citrulline every day might lower your bottom blood pressure number by about 3 points, but taking less than that doesn’t seem to do anything noticeable.

In hypertensive postmenopausal women, increases in blood flow to the forearm during hand exercise after taking L-citrulline are linked to improved dilation of the brachial artery, suggesting that the lining of blood vessels plays a role in how blood flow responds to exercise.