What happens when you take losartan with hawthorn?
Losartan is an angiotensin II receptor blocker (ARB). Hawthorn (Crataegus monogyna, Crataegus laevigata) is a traditional cardiovascular herb taken for blood pressure and mild heart symptoms. The two lower blood pressure by different routes, and when taken together those effects can add up.
- Losartan blocks a pressure pathway. It blocks the angiotensin II type 1 receptor, which reduces vascular constriction and the fluid retention driven by aldosterone.
- Hawthorn relaxes vessels by a separate route. Its extracts appear to promote endothelial nitric oxide release and modulate vascular tone, producing a modest blood-pressure-lowering effect of their own.
- The effects stack. Because both reduce vascular tone through different mechanisms, the combined drop can be a little larger than either one alone.
- Occasionally that is enough to feel. In people who already run low, or who take several blood pressure medicines, the extra drop can show up as dizziness or lightheadedness, especially on standing.
This is not a dangerous chemical clash. Unlike some ARB interactions, hawthorn does not raise potassium or stress the kidneys. The only practical concern is additive blood pressure lowering, and for most people on a stable losartan dose it is mild.
Why is this important?
The risk here is low, not severe. But the additive blood-pressure effect matters in a few specific situations worth knowing about.
The first is people whose blood pressure is already well controlled on losartan. If your readings already sit comfortably, an additional small drop from hawthorn can occasionally tip into territory where you feel dizzy on standing. In older adults that lightheadedness is the thing to watch, because of the fall risk it carries.
The second is people on more than one blood pressure medication. If losartan is paired with a diuretic, calcium channel blocker, or beta blocker, your baseline may already be near the lower end of target, so any further lowering is more likely to be noticeable.
The third is simply that hawthorn is often added quietly. People start a cardiovascular supplement without mentioning it, then attribute any new dizziness to their underlying condition rather than to the supplement, which delays sorting it out. Independent interaction databases list no documented losartan-hawthorn interaction; the additive blood-pressure effect is plausible and worth a mention, but it should not be overstated.
What should you do?
This combination is generally manageable. The sensible approach is to keep your prescriber in the loop and pay attention to how you feel rather than to self-adjust anything.
- Before you start hawthorn: tell your prescriber or pharmacist you plan to add it, so they can decide whether your particular medication mix and clinical situation make sense, and whether some home blood pressure checks during the introduction are worthwhile.
- In the first few weeks, every day: if your prescriber suggests it, take home blood pressure readings at the same time of day, sitting after a few minutes of rest with your feet flat, using the same arm and a validated cuff. Note any dizziness or lightheadedness, particularly when you stand up.
- After any change, and if symptoms appear: if your readings run unusually low, or you feel dizzy on standing, contact your prescriber rather than adjusting the hawthorn or the losartan yourself. A change to the prescription medication may be reasonable, but that is a clinical decision.
Avoid starting hawthorn during acute illness, dehydration, or right after another medication change, when blood pressure is already in flux. People with significant heart failure, severe aortic stenosis, or any condition where blood pressure stability is critical should not add hawthorn without explicit cardiology input.
Which specific products are affected?
Standardized hawthorn extracts are the most relevant, because they concentrate the active compounds and are usually labeled by their procyanidin or flavonoid content. WS 1442 is the most-studied extract and appears in much of the clinical trial literature. These standardized products are the ones most likely to produce a measurable blood-pressure effect.
Hawthorn berry teas, tinctures, and dried whole-berry capsules are less concentrated and less likely to matter, though large daily volumes can still contribute. Combination cardiovascular supplements often pair hawthorn with ingredients such as CoQ10, magnesium, garlic, or arginine; check the full formula, because several mild blood-pressure-lowering ingredients together can add up to more than the hawthorn alone.
The science behind it
A 2025 meta-analysis of randomized, placebo-controlled trials (Szikora Z, et al., PMID 40732315) found that hawthorn produces a clinically meaningful reduction in blood pressure in hypertension, on the order of a few mmHg in systolic pressure on average. That establishes hawthorn as a genuine, if modest, blood-pressure-lowering agent on its own.
What the evidence does not show is a specific, quantified interaction with losartan. Independent interaction databases (Drugs.com) report no documented losartan-hawthorn interaction and note only a theoretical additive blood-pressure-lowering effect. So the mechanism and the low severity are well supported, but any precise figure for how much extra blood pressure falls when the two are combined would be going beyond what the data actually show.
Frequently Asked Questions
Is it dangerous to take hawthorn with losartan?
For most people on a stable losartan dose it is not dangerous. The main effect is that both can lower blood pressure, so they may add up and occasionally cause dizziness. There is no documented serious interaction.
Will hawthorn make my losartan stop working?
No. Hawthorn does not block losartan; if anything it nudges blood pressure in the same direction. The concern is additive lowering, not reduced effectiveness.
Can I take them at different times of day to avoid the interaction?
Spacing the doses does not remove an additive blood-pressure effect, because both act over the course of the day. The useful step is watching how you feel and keeping your prescriber informed, not timing.
What symptoms should make me call my prescriber?
Dizziness or lightheadedness, especially on standing, near-fainting, or blood pressure readings that run unusually low for you. Contact your prescriber rather than changing doses yourself.
Does hawthorn affect potassium or my kidneys like some blood pressure interactions?
No. Unlike potassium supplements or salt substitutes, hawthorn does not raise potassium or stress the kidneys with losartan. Its only relevant effect here is on blood pressure.
Should I stop hawthorn before surgery or if I get sick?
It is reasonable to be cautious during acute illness, dehydration, or around surgery, when blood pressure can swing. Tell your care team you take it and follow their advice.
Key takeaways
- Hawthorn modestly lowers blood pressure on its own; losartan lowers it too, so the effects can add up.
- Severity is low: there is no documented serious losartan-hawthorn interaction, and no effect on potassium or kidneys.
- The main thing to watch is dizziness or lightheadedness, especially on standing, and especially if you take more than one blood pressure medication.
- Tell your prescriber or pharmacist before adding hawthorn, and do not change either dose on your own.
- Standardized extracts (like WS 1442) matter most; teas and tinctures are weaker but can still contribute.