Yes, water fasting can lower blood pressure for some people in the short term, but it carries health risks and needs medical guidance.
People with high blood pressure sometimes hear claims that strict water only fasts can bring numbers down fast. Stories from clinics and retreat centers can sound persuasive, especially when they mention coming off medicine after a few weeks of living on water.
This guide looks at what research shows about water fasting and blood pressure, how safe this approach is, and how it compares with everyday habits such as DASH eating, weight loss, and exercise.
How Water Fasting Affects Blood Pressure
Water fasting usually means drinking only water for several days or weeks, often in a clinic that watches blood tests and symptoms. When food stops, the body sheds sodium and water, burns stored glycogen, and starts drawing on fat and muscle. Those shifts change blood volume and body weight, which both influence blood pressure.
Rapid loss of salt and water lightens the fluid load in blood vessels. Weight drops over days, which can ease pressure on artery walls. Insulin levels fall, which may improve how the kidneys handle sodium. Some research also points to calmer sympathetic nervous system activity.
| Study | Fasting Approach | Blood Pressure Change |
|---|---|---|
| TrueNorth trial 2024 | About 11 day water only fast plus plant based refeed | Average pressure under 130/80 mmHg; many stopped tablets |
| Water fasting follow up | Prolonged water fast with planned refeed | Median drop near 19/5 mmHg at six weeks; less medicine at 12 months |
| Narrative review 2023 | Fasts of 5–20 days on water or near zero calories | Modest average pressure falls with 2–10% weight loss |
| Older clinic case series | Water only fasts in residential centers | Large short term drops; little long term tracking |
| Intermittent fasting umbrella review | Time restricted and alternate day fasting | Small average reductions in systolic and diastolic pressure |
| Intermittent fasting scoping review | Mixed fasting patterns in metabolic syndrome | Better abdominal fat, pressure, and insulin sensitivity in several trials |
| DASH plus time restricted eating trial | Six weeks of DASH alone versus DASH with eating window | Both lowered pressure; time restricted plan tended to drop more |
Does Water Fasting Reduce Blood Pressure Safely Over Time?
Taken together, published trials suggest that medically supervised water only fasting can reduce blood pressure, especially in people with stage 1 or stage 2 hypertension. In the TrueNorth trial, nearly all participants left the program with readings in the normal range and no blood pressure tablets at discharge.
That result came from a narrow setting: a residential clinic, close daily monitoring, an average of 11 fasting days, a careful plant based refeed, and careful selection of people who were stable enough for intensive fasting. Outside that setting, the same fast can be unsafe. Rapid drops in blood pressure, shifts in electrolytes, and changes in kidney function can cause lightheadedness, fainting, or worse, especially in people who use blood pressure drugs, diabetes drugs, or diuretics.
Experts who work in supervised fasting programs advise that anyone thinking about a prolonged water fast talk with their doctor first and, if cleared, only attempt it in a setting that can track blood tests, symptoms, and medication needs during the fast and refeed phase.
Short Term Versus Long Term Blood Pressure Effects
The clearest effect of water fasting on blood pressure shows up during the fast and shortly after refeeding. Loss of fluid, lower sodium, lower insulin, and weight change all show up quickly on a home blood pressure monitor.
Follow up data from supervised programs suggest that part of the drop can persist for at least six weeks, especially when people stay with a low salt, whole plant pattern. At the same time, the evidence base is still small, with few randomized trials that compare water fasting directly with standard care, so this approach sits in the experimental column, not as routine blood pressure treatment.
Risks And Limits Of Water Only Fasts
Water only fasts are tough on the body. Energy intake drops to zero, protein and micronutrients stop coming in, and lean tissue can be broken down for fuel. In one review of fasts lasting up to 20 days, about two thirds of the weight loss came from lean mass instead of fat, which raises concerns about muscle loss and long term strength.
Short term issues can include fatigue, headaches, nausea, low blood sugar symptoms, gout flares, and sleep changes. People with kidney disease, heart rhythm problems, eating disorders, pregnancy, breastfeeding, or type 1 diabetes face extra risk and should stay away from water only fasts aimed at blood pressure control.
Blood pressure medicines, diabetes tablets, and diuretics can also become too strong once food intake stops, since pressure and glucose levels are already falling from the fast. In clinical programs, physicians usually adjust or pause these drugs and check patients daily. Trying to copy that approach at home without medical oversight can lead to sudden drops in pressure, loss of consciousness, or severe electrolyte imbalance.
Where Water Fasting Fits Among Other Blood Pressure Tools
Major heart groups still place proven lifestyle steps at the center of blood pressure care. Core steps include weight loss when needed, heart friendly eating, low sodium intake, regular activity, and tobacco avoidance. Medicine still matters when lifestyle changes do not bring readings into a safe range.
Within that plan, water fasting sits as a niche option for a small group of patients in specialist centers, while milder fasting patterns fit more easily into daily life. The table below sets water fasting beside other lifestyle tools that have stronger long term data.
| Strategy | Blood Pressure Effect | Practical Notes |
|---|---|---|
| Water only fasting | Large short term drops in supervised trials | Intense; needs close medical oversight and careful refeed |
| DASH style diet | Systolic pressure often falls by about 10 mmHg | Fruit, vegetables, whole grains, low fat dairy; less sodium and processed meat |
| Weight loss of 5–10% | Each kilogram lost can cut systolic pressure by around 1 mmHg | Best reached through a moderate, steady calorie gap |
| Daily sodium reduction | Lowering salt to guideline levels can drop systolic pressure by 5–6 mmHg | Cook at home more often, choose low sodium labels, limit packaged foods |
| Regular aerobic exercise | 30 minutes on most days can lower resting pressure by several mmHg | Walking, cycling, or swimming; start from your current level |
| Time restricted eating | Small average reductions in pressure across many trials | Keeps meals within an 8–10 hour daytime window |
| Limiting alcohol intake | Helps blunt spikes in blood pressure | Set weekly drink limits and mix in alcohol free days |
Safer Everyday Strategies For Lower Blood Pressure
For most people with raised blood pressure, the biggest gains come from steady, repeatable habits instead of brief, intense interventions. A heart focused eating plan such as DASH brings in potassium rich fruit and vegetables, whole grains, and low fat dairy while trimming sodium and added sugars. The American Heart Association promotes this style of eating for blood pressure control.
Alongside food choices, routine movement matters. Even a brisk 20 to 30 minute walk on most days can help lower blood pressure and help with weight management. Strength training two or three times per week protects muscle.
Who Should Avoid Water Fasting For Blood Pressure
Some groups face clear hazards with water only fasting and should steer toward other approaches. These include people with type 1 diabetes, serious kidney disease, liver disease, eating disorders, recent heart attack or stroke, pregnancy, breastfeeding, or a history of fainting with low blood pressure.
People who take several blood pressure medicines, insulin, or other glucose lowering drugs also face higher risk, since these medicines can overshoot once food intake stops. Older adults, especially those with frailty or baseline weight loss, are at special risk for muscle loss and falls during and after a strict fast.
If you fall into any of these groups, or if you are unsure, use safer, guideline supported steps such as moderated calorie intake, salt reduction, and regular movement instead of experimenting with prolonged water only fasts.
Balanced View On Does Water Fasting Reduce Blood Pressure?
So, does water fasting reduce blood pressure? Under medical supervision in selected patients, prolonged water only fasting can bring large short term drops in blood pressure, sometimes enough to move stage 1 or 2 hypertension back into the normal range and allow medicine withdrawal for a time.
At the same time, strict water fasting carries real risks, is hard to repeat, and depends heavily on what happens after the fast. For most people with high blood pressure, steady changes in diet, movement, salt intake, body weight, and medication use remain the safest and most reliable route. Water fasting belongs, if at all, in a small corner of care plans shaped and monitored by health professionals, not as a do it yourself cure.