Melatonin is a natural sleep supplement often used for those with jet lag or other disorders related to circadian rhythms. However, it is possible that in addition to regulating sleep, it may be a useful treatment for some chronic conditions, including high blood pressure. While there is some evidence that it may be effective for blood pressure symptoms, melatonin can also interfere with some blood pressure medications. Be sure to check with your doctor first.

The hormone melatonin plays a role in people's sleep patterns, and may regulate both when people fall asleep and how long they remain asleep. Melatonin occurs naturally in your body, and its levels tend to be highest during the time when you would be more inclined to sleep: at night, when it is dark. Supplemental melatonin may induce sleep for some people and is often used by people on late work shifts or when changing time zones. It can be purchased over the counter without a doctor's prescription; however, this does not mean it is completely safe for everyone. Like any other supplement, melatonin may have side effects for some people, and it can interact with some medications.

Melatonin may also be effective at regulating other bodily functions aside from sleep. Researchers have begun to investigate whether or not melatonin can improve blood pressure readings for those with hypertension. A review in the 2011 issue of "Vascular Health and Risk Management," confirms that there have been several studies on the relationship of melatonin and night blood pressure, and the results are promising, especially for nighttime blood pressure regulation. During the day, however, any effect on blood pressure was minimal. In addition to its potential for blood pressure regulation, melatonin may improve sleep for some people who take medications to control their high blood pressure. Certain blood-pressure-regulating medications like beta blockers may interfere with sleep. While melatonin has been studied for its effect on those who use blood pressure medications, the current evidence that it improves sleep for this population is inconclusive. If you are on blood pressure lowering medication, do not take melatonin without your doctor's consent, as it could cause your blood pressure to go too low which could result in shock and serious health consequences, according to the American Heart Association.

While it may improve some symptoms, people who have high blood pressure may need to avoid melatonin altogether, as it can interact with some of the medications they use. Melatonin can reduce the effectiveness of common blood pressure medications, including both methoxamine and clonidine. In fact, MedlinePlus recommends those with high blood pressure avoid melatonin altogether, as its use may raise blood pressure for some people, which can be dangerous for those who already have problems with their blood pressure regulation. In addition, melatonin can interfere with blood thinners and sedatives, which some people with high blood pressure take routinely.

Because of its ability to promote sleep, melatonin should be taken before bedtime. Doctoroz.com recommends taking 0.3 to 1 milligram of melatonin an hour and a half before bedtime. The website warns that taking too much melatonin -- more than 1 milligram -- may have an adverse effect and end up disrupting your sleep cycle. Lack of sleep may in turn raise your blood pressure according to the American Heart Association.

The jury is still out on melatonin's effects on blood pressure. If you have high or low blood pressure, or take medications to control your blood pressure, it is best to avoid the supplement unless advised otherwise by your doctor. Even though some blood pressure medications may cause sleep disturbances, you should never take any sleep aids, including melatonin, without talking to your doctor first. The results could be harmful to your health.