Blood pressure changes on a GLP-1

Two separate findings

People who ask about blood pressure on a GLP-1 usually mean one of two things. Some have read that these medicines lower it and want to know by how much. Others feel light-headed and wonder whether their pressure is now too low. The labels answer the first in section 14, the clinical studies, where blood pressure is a secondary measurement next to weight, and the second in section 6, where hypotension is listed as an adverse reaction ^[1][2].

Not every label has both. The US Mounjaro® and Ozempic® labels, which describe type 2 diabetes trials, have no hypotension entry and no blood pressure table ^[5][6]. For tirzepatide, the weight-loss data sit in the Zepbound® label and, in Europe, in the Mounjaro® product information ^[2][7].

How much blood pressure fell in the trials

The table shows the change in systolic pressure, the upper number, from the start to the end of each main trial. Starting averages were about 123 to 131 mm Hg, so most participants did not have high blood pressure at entry.

• Diastolic pressure, the lower number, moved less: the European Mounjaro® summary reports about −4 mm Hg in the weight trials against under 1 on placebo, and up to −9/−3 mm Hg in the SURPASS-CVOT heart trial ^[7].
• The Wegovy®, Zepbound® and Foundayo™ labels mark these blood pressure results as outside their main pre-specified statistical testing, so they describe what was seen rather than prove an effect ^[1][2][4].

When pressure drops too low

Hypotension rows count reports of low blood pressure, a drop on standing (orthostatic hypotension) and, in some labels, “blood pressure decreased”. They are reports made during the trials, not routine readings below a fixed number.

• The Wegovy® label adds that adolescents on the medicine had more hypotension than adults on it ^[1].

What studies outside the labels show

A 2023 systematic review pooled six randomised placebo-controlled trials of semaglutide for weight reduction in 4,744 adults without diabetes. Average blood pressure at the start was in the normal range. Systolic pressure ended 4.83 mm Hg lower and diastolic 2.45 mm Hg lower than with placebo ^[8]. The authors judged the trials to be of high quality, but they also stated that the effect in people with obesity and high blood pressure had not yet been worked out; the trials were not designed to test that.

Two semaglutide studies looked at what happens when treatment ends. In STEP 4, people switched to placebo after a 20-week run-in saw systolic pressure climb back and finished 3.9 mm Hg higher than those who stayed on semaglutide ^[9]. A year after STEP 1 ended, the extension study reported that the cardiometabolic improvements had moved back towards their starting values, alongside regain of about two-thirds of the weight lost ^[12]. What stopping means more broadly has its own article.

People already taking blood pressure medicines

This is where the labels are most specific. Low blood pressure was more frequent in people on medicine for high blood pressure: 2.2% against 1.2% among Zepbound® users with and without that treatment, and 4% against 1% with Foundayo™ ^[2][4]. The Wegovy® label says the same without figures ^[1]. The Canadian Zepbound® monograph splits the numbers by dose; with blood pressure treatment they rose from 0.5% on 5 mg to 3.4% on 15 mg ^[10].

MedlinePlus lists diuretics and heart medicines used for high blood pressure among the medicines that can lower blood pressure, and says that if a medicine is the cause, your provider may change the dose or switch it; it also says not to stop any medicine before talking to them ^[13]. As weight and readings change on a GLP-1 medicine, that review is a conversation for your prescriber, not a change to make alone.

Why it may happen

• Supported by the labels: some episodes of low blood pressure came together with stomach side effects and loss of body fluid, and the labels link vomiting and diarrhea with dehydration ^[1][2][10].
• Supported by the labels: average blood pressure fell alongside weight in the weight trials, and adding a medicine that lowers pressure on top of existing treatment was linked with more hypotension ^[1][2][4].
• Proposed but not measured: the 2023 meta-analysis authors suggest that reducing excess weight may be a way to lower blood pressure ^[8]. The labels and abstracts we used do not separate an effect of weight loss from any direct effect of the medicine.
• General background: MedlinePlus lists not drinking enough, nerve damage from diabetes, heart rhythm changes and heart failure among other causes of low blood pressure ^[13]. Dehydration can follow vomiting, diarrhea, fever or simply not feeling like drinking when nauseated ^[15].

What low blood pressure feels like, and other causes

MedlinePlus puts normal adult blood pressure between 90/60 and 120/80 mm Hg and says a drop of as little as 20 mm Hg can cause problems for some people ^[13]. Symptoms can include blurry vision, confusion, dizziness, light-headedness, fainting, nausea, sleepiness and weakness. A drop on standing usually lasts only seconds to minutes; when it follows a meal it is called postprandial hypotension and is most common in older adults ^[13].

Not every dizzy spell is low blood pressure. Low blood sugar, dehydration and inner ear problems can feel similar, and the GLP-1 dizziness article sets out how they differ. In older adults, falls caused by low blood pressure can lead to hip or spine fractures, which is one reason to mention fainting or near-fainting promptly ^[13].

What may help, and keeping home readings

When low blood pressure causes symptoms, MedlinePlus suggests sitting or lying down straight away and raising the feet above heart level. To prevent symptoms, a provider may suggest drinking more fluids, getting up slowly after sitting or lying down, avoiding alcohol and, in some cases, compression stockings ^[13]. The Medication Guides note that drinking fluids lowers the chance of dehydration during stomach side effects ^[1].

If your prescriber asks for home readings, MedlinePlus describes resting first, sitting with the back supported and the arm at heart level, taking more than one reading and noting the time. It adds that home readings are often a better guide than office ones, and that it is worth asking your provider to compare your home readings with those taken at the clinic ^[14].

Wegovy®, Ozempic® and Saxenda® are registered trademarks of Novo Nordisk A/S. Zepbound® and Mounjaro® are registered trademarks and Foundayo™ is a trademark of Eli Lilly and Company. PepLabo is not affiliated with or endorsed by Novo Nordisk or Eli Lilly and Company.

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