Drinking tea can raise your blood pressure, but the spike is normally temporary and peaks 45 to 90 minutes after ingestion, according to the "American Journal of Hypertension," If you have hypertension, or high blood pressure, the effect may be more acute, particularly if you are taking beta-blockers, metoprolol or propranolol to control your hypertension. For an accurate home blood pressure reading, ensure that your device cuff fits correctly. Calibrate it against a reading in your doctor's office. Do not eat or drink tea, coffee or alcohol for at least 45 minutes prior to taking a measurement.
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Your blood pressure varies naturally throughout your day. Hypertension is when your blood pressure stays high most of the time. You may have hypertension and have absolutely no symptoms. According to the National Heart, Lung and Blood Institute, 22 percent of Americans are unaware that they suffer from the condition. If you think that drinking tea is affecting your blood pressure, have your pressure checked by your physician and begin monitoring it at home. You may have high blood pressure if your systolic pressure, the top number, is more than 120, or your diastolic pressure, the bottom number, is higher than 80.
Tea contains caffeine, a stimulant that can increase your blood pressure. According to the National Institutes of Health website MedlinePlus, this is more likely to occur if you already have hypertension or if you do not regularly consume products with caffeine. If you are otherwise healthy, the effect of caffeine will likely be fleeting. There are some people who are particularly sensitive to the effect of caffeine. In the May 2005 issue of the "American Journal of Hypertension," Dr. Noha H. Farag writes that up to 50 percent of the general population will feel the effects of caffeine each time they ingest it.
An 8-ounce cup of brewed black tea has about 42 to 72 milligrams of caffeine, more than green tea, but less than the same serving size of coffee. Ingesting 95 mg of caffeine can spike your blood pressure three to 14 points. Based on that assessment, drinking two or more cups of black tea would provide more than enough caffeine to affect your blood pressure.
A 6-ounce serving of green tea has about 26 grams of caffeine. As with black tea, the total caffeine content in multiple servings can impact your blood pressure, but green tea may also provide you with some protection against heart disease. In the July 26, 2004 issue of the "Archives of Internal Medicine," Dr. Yi-Ching writes that in a study of 600 habitual green or oolong tea drinkers, those who drank 120 to 599 milliliters per day, decreased their risk of developing hypertension by 46 percent. Those who drank 600 milliliters or more per day further reduced their risk.