How Long Does Losartan Take To Work?
In our latest question and answer, our pharmacist discusses how long it takes losartan to start working to reduce blood pressure.
How long does it take for losartan to start taking effect on high blood pressure?
May 18, 2023- Losartan begins working right away to lower blood pressure, though full effects take a few weeks.
- Your doctor will typically check how well the medication is working after about 4 weeks to decide if any changes to your treatment are needed.
- Many people need more than one blood pressure medication along with lifestyle changes to reach their blood pressure goals.
Answer
Losartan (generic for Cozaar) will begin to work right away in regard to lowering your blood pressure, which is why some folks experience certain side effects, like dizziness and lightheadedness, when therapy is started.
However, depending on how high your blood pressure was when you started the drug, your doctor will generally reevaluate you and your therapy needs after around 4 weeks of consistent dosing. At this point they will determine whether or not additional interventions need to be made for you.
Detailed Information
Losartan is an angiotensin II receptor antagonist, a drug class commonly referred to as an 'ARB' (angiotensin II receptor blocker). ARBs are commonly used to treat hypertension (high blood pressure) and work by blocking the action of a hormone that causes blood vessels to narrow, thus helping to relax and widen the blood vessels.
As mentioned in the first section, losartan will begin working with the first dose, but full effects will generally take at least a few weeks.
When you first start taking losartan, your pharmacist should warn you about some common side effects, many of which are related to an initial drop in blood pressure.
These side effects include dizziness, lightheadedness, and 'orthostatic hypotension', which signifies a drop in blood pressure when you change positions, especially when you stand up from a sitting or lying down position.
Being Re-Evaluated After Starting Losartan
According to the American College of Cardiology (ACC)/American Heart Association (AHA) 2017 hypertension guideline, individuals who are treated with antihypertensive drugs, like losartan, should be evaluated every four weeks or so until their blood pressure reaches the target goal.
In other words, after you start taking losartan, your doctor will likely reevaluate your blood pressure, and how the drug is working for you, after about 4 weeks. The reason for this timeframe is that it allows enough time for long-acting antihypertensive drugs like losartan to manifest their full blood pressure-lowering effect while keeping in mind that many individuals require additional interventions if blood pressure is still not at goal.
It should be noted, however, for patients with severely elevated blood pressure, reevaluating at two weeks or even sooner may be necessary.
Below is a flowchart provided from the AHA hypertension guidelines I have hyperlinked above, showing the recommendation for a re-evaluation timeframe of 4 weeks:

Will Losartan Itself Help You Reach A Normal Blood Pressure?
It's important to remember that achieving blood pressure control can be a gradual process. Depending on how high your blood pressure is and how your body responds to losartan, it may take some time to determine the appropriate dosage and its effectiveness for you personally and everyone's response to medications can vary.
It's also important to point out that many studies show that only 25-50% of individuals achieve blood pressure control with lifestyle modifications and monotherapy (i.e., only one blood pressure medication) alone. Oftentimes, additional medications need to be added on if you aren't able to reach your goal blood pressure with one medication and changes to your lifestyle.
Be sure to keep regular appointments with your doctor and keep in touch with them regarding how you are doing in reaching your blood pressure goals.
Final Words
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References & sources
- 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA Guideline for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines — PubMed
- Cozaar Prescribing Information — AccessFDA
Glossary — Terms in This Answer
- Angiotensin II receptor antagonist
- A type of blood pressure medication that blocks hormones from narrowing blood vessels, allowing them to relax and widen.
- ARB
- Short for angiotensin II receptor blocker, a class of blood pressure medications.
- Hypertension
- The medical term for high blood pressure.
- Orthostatic hypotension
- A sudden drop in blood pressure that occurs when you change positions, especially when standing up from sitting or lying down.
- Antihypertensive drugs
- Medications used to treat high blood pressure.
- Monotherapy
- Treatment using only one medication to manage a condition.