7 Shocking Losartan Side Effects You Must Know Today

January 26, 2026 Admin

If you take losartan or losartan potassium, you are not alone. Millions rely on this medication for blood pressure and kidney protection. Yet many people have never been told about the most concerning losartan side effects.

You deserve to understand what your medicine might do, both the benefits and the risks. This guide breaks everything down in clear, calm language. 💊

Table of Contents

What Is Losartan, Exactly?

Losartan is a prescription drug used mainly to:

Treat high blood pressure (hypertension).
Protect the kidneys in people with diabetes and protein in the urine.
Help certain patients with heart failure.

It belongs to a group called ARBs, or angiotensin II receptor blockers.

How it works, in simple terms:

Your body makes a hormone called angiotensin II.
That hormone tightens blood vessels and raises blood pressure.
Losartan blocks this effect, so blood vessels relax and pressure drops.

You may see it listed as losartan potassium on your pill bottle. Potassium is just the salt form used to make the tablet.

To learn more about the science behind what is losartan, you can read the Mayo Clinic overview here:
what is losartan

Losartan works very well for many people. Most side effects are mild, if they appear at all. Still, some reactions can be serious or even life‑threatening.

Let’s walk through seven of the most important risks to know.

7 Shocking Losartan Side Effects You Must Understand

Not everyone will experience these reactions. Some are rare.
However, knowing the warning signs can help you act quickly if something feels wrong. 🚨

1. Dangerous Drops in Blood Pressure (Dizziness and Fainting)

One of the most notable side effects of losartan is low blood pressure, called hypotension.

This can happen especially:

When you first start losartan.
When your dose increases.
If you are dehydrated from vomiting, diarrhea, or heavy sweating.
If you take other blood pressure medications or diuretics (“water pills”).

Symptoms to watch for:

Sudden dizziness when standing.
Feeling lightheaded or “about to black out.”
Blurred vision.
Fainting or near‑fainting episodes.

Real‑life example:
Maria, 62, started losartan for high blood pressure. Two days later, she stood up quickly from bed and felt the room spin. She grabbed a chair to avoid falling and checked her pressure. It was much lower than usual.

What to do:

Sit or lie down right away if you feel faint.
Rise slowly from bed or chairs.
Drink enough fluids, unless your doctor restricts them.
Call your doctor if dizziness is frequent or severe.
Go to emergency care if you faint, hit your head, or cannot stay awake.

Low blood pressure can be serious, especially in older adults. It raises fall risk and injury risk.

2. High Potassium Levels That Affect the Heart

Losartan can increase potassium in your blood. This condition is called hyperkalemia.

Most people never notice mild changes.
But very high potassium can disturb your heart rhythm and become dangerous. ❤️

You are at higher risk if you:

Have kidney disease.
Take potassium supplements or salt substitutes with potassium.
Use other medicines that raise potassium, like some diuretics or ACE inhibitors.

Symptoms of high potassium:

Muscle weakness or heavy, tired muscles.
Tingling or numbness in hands, feet, or lips.
Heart palpitations or skipped beats.
Sudden chest pain or shortness of breath.

What helps reduce risk:

Do not start potassium supplements without medical advice.
Ask your doctor before using salt substitutes.
Keep all scheduled blood tests to check potassium and kidney function.

Call your doctor right away if you notice new palpitations or muscle weakness.
Seek emergency care for chest pain, severe shortness of breath, or fainting.

3. Kidney Function Changes or Sudden Kidney Injury

This one may feel surprising.
Losartan is often used to protect kidneys, especially in diabetes. Yet it can still affect kidney function in some people.

Why this happens:

Losartan changes blood flow within the kidneys.
In vulnerable patients, this can sometimes reduce filtration too much.

Higher risk groups include:

People with narrowed kidney arteries.
Those with severe heart failure.
Anyone already living with advanced kidney disease.
People taking NSAIDs long term, like ibuprofen, naproxen, or diclofenac.

Warning signs of kidney problems:

Swelling in legs, ankles, feet, or around the eyes.
Sudden weight gain from fluid retention.
Urinating much less than usual.
Foamy urine or dark‑colored urine.
Extreme fatigue or nausea.

Your doctor will usually order blood tests to monitor:

Creatinine (a marker of kidney function).
Estimated GFR (a measure of filtration).

Do not stop losartan on your own.
Instead, contact your doctor quickly if you notice swelling, decreased urine, or sudden fatigue.

Table: Common vs Serious Reactions to Losartan

Symptom / Effect	How Common?	What It Might Mean	What You Should Do
Mild dizziness	Fairly common	Blood pressure lowering	Stand up slowly, call doctor if severe
Headache	Common	Body adjusting to medication	Track pattern, mention at next visit
Cough	Less common than with ACE inhibitors	Throat irritation or sensitivity	Call doctor if persistent
Swelling of face or tongue	Rare but serious	Possible angioedema or allergy	Call emergency services immediately
Severe fatigue or weakness	Less common	Low pressure, kidney or potassium changes	Call doctor urgently
Chest pain or palpitations	Uncommon but urgent	Heart rhythm problem or other disease	Seek emergency care
Very little urine	Uncommon but serious	Possible kidney injury	Contact doctor or emergency care

4. Serious Swelling Reactions (Angioedema)

Angioedema is one of the most frightening potential losartan side effects, even though it is rare.

This reaction involves sudden swelling under the skin, often around:

The lips.
The tongue.
The face and eyelids.
Sometimes the throat.

It can happen:

Soon after starting losartan.
Or unexpectedly after months or years of use.

Symptoms of angioedema:

Rapid swelling of lips, tongue, or face.
Trouble breathing or noisy breathing.
Trouble swallowing or speaking.
Tightness in the throat.

This is a medical emergency.

If you notice swelling of your face, lips, or tongue:

Call emergency services right away.
Do not wait to see if it improves.
Do not take another dose until a doctor evaluates you.

After angioedema, doctors usually avoid losartan and similar medications in the future.

5. Severe Allergic Reactions and Skin Problems

Some people develop allergic responses unrelated to angioedema.
These reactions can affect the skin, lungs, or entire body.

Possible signs:

Rash, hives, or red itchy patches.
Peeling or blistering skin.
Swelling of hands, feet, or joints.
Wheezing, chest tightness, or difficulty breathing.
Fever with rash or sore throat.

One rare but serious condition is Stevens–Johnson syndrome.
It causes flu‑like symptoms with painful skin blistering.

What to do:

For mild rash, call your doctor soon for advice.
For rash plus fever, blisters, or breathing issues, seek emergency care.

Take photos of the rash if possible.
These can help your doctor identify the reaction. 📷

6. Harm to an Unborn Baby During Pregnancy

This is one of the most critical losartan side effects to understand.

Losartan should not be used during pregnancy.
It can cause serious harm to an unborn baby, especially in the second and third trimesters.

Potential risks include:

Poor development of the baby’s kidneys.
Low amniotic fluid levels.
Skull and limb development problems.
Death of the fetus in severe cases.

Because of this, losartan carries a strict warning for pregnancy.

If you could become pregnant:

Talk with your doctor about safe birth control while taking losartan.
If you plan pregnancy, ask about alternative medications.
If you become pregnant while taking losartan, contact your doctor immediately.

Do not panic, but do act quickly.
Your doctor will usually stop losartan and switch you to a safer option.

Losartan also is not recommended while breastfeeding in many cases.
Discuss risks and benefits with your healthcare provider.

7. Extreme Tiredness, Chest Symptoms, or Mood Changes

Some reactions are harder to link directly to losartan.
Yet they can still signal trouble and should never be ignored.

Concerning symptoms can include:

Sudden, heavy fatigue or exhaustion.
Shortness of breath with light activity.
New chest pain or tightness.
Fast, slow, or irregular heartbeat.
Confusion or feeling “not like yourself.”
New anxiety or feeling unusually low.

These issues may come from several possible causes:

Very low blood pressure.
Kidney or electrolyte changes.
Underlying heart disease becoming more obvious.
Rare liver or muscle problems.

When to call your doctor quickly:

You are too tired to perform basic daily tasks.
Breathing feels more difficult over days or weeks.
You notice yellow eyes, dark urine, or severe abdominal pain.

When to seek emergency help:

Chest pain or pressure.
Sudden severe shortness of breath.
Confusion, slurred speech, or weakness in an arm or leg.

Even if losartan is not the only cause, these symptoms always deserve urgent attention.

Who Is at Higher Risk for Serious Losartan Reactions?

While anyone can experience problems, some groups face more danger.

Higher‑risk groups include:

Older adults, especially over 65.
People with chronic kidney disease.
Individuals with narrowed arteries to the kidneys.
Those on multiple blood pressure medications.
People taking NSAIDs regularly for pain.
Patients with heart failure or advanced heart disease.
Pregnant women or those planning pregnancy.

If you are in any of these groups, ask your doctor:

How often do I need blood tests?
What exact symptoms should make me call you?
Are there alternative medications if problems appear?

Being proactive does not mean you will have serious losartan side effects.
It simply means you are informed and prepared. ✅

How to Talk With Your Doctor About Losartan

It can feel intimidating to question a prescription.
However, open communication helps you stay safe and involved in your own care.

Consider asking:

Why did you choose losartan instead of another option?
What benefits should I expect, and how soon?
Which side effects of losartan are most important for me personally?
How often should we recheck my blood pressure and labs?
What should I do if I miss a dose?

Bring a written list of your:

Other medications and supplements.
Over‑the‑counter pain relievers you use.
Salt substitutes or herbal products.

This helps your doctor spot possible interactions or risks early.

For a medical reference on side effects of losartan, including detailed lists, you can review MedlinePlus here:
side effects of losartan

Practical Tips to Use Losartan More Safely

You cannot remove every risk, but you can reduce many of them.

Daily habits that help:

Take losartan at the same time each day.
Check blood pressure regularly at home.
Keep a simple symptom diary.
Stay hydrated unless your doctor says otherwise.
Limit alcohol, which can drop blood pressure further.

Medication safety steps:

Avoid starting or stopping other drugs without medical advice.
Tell every healthcare provider that you take losartan potassium.
Ask your pharmacist to check for interactions.

When to schedule extra follow‑up:

After any dose change.
After dehydration from illness or heat.
If you notice new swelling, dizziness, or weakness.

These small steps can protect you from many potential losartan side effects. 🛡️

FAQs About Losartan and Its Side Effects

1. Is losartan safe to take long term?

Many people use losartan for years without major problems.
Regular checkups and blood tests are important for long‑term safety.
Your doctor will weigh benefits against any emerging risks over time.

2. Can I stop losartan if I feel side effects?

Do not stop losartan suddenly without guidance.
Stopping abruptly can raise blood pressure and strain your heart.
Call your doctor first to discuss alternatives and a safe taper plan.

3. Are losartan and losartan potassium different?

They refer to the same medication.
“Losartan potassium” is the full chemical name used for tablets.
Doctors usually shorten it to “losartan.”

4. Does losartan cause cough like some other blood pressure drugs?

Losartan can cause cough in a few people, but it is less common.
ACE inhibitors like lisinopril cause cough more frequently.
If your cough is persistent, talk with your doctor about options.

5. Is it safe to drink alcohol while taking losartan?

Alcohol can lower blood pressure further.
You may feel dizzy or lightheaded more easily.
Moderation is key, and some people may need to avoid alcohol completely.

6. How will I know if losartan is harming my kidneys?

You may notice swelling, changes in urination, or extreme fatigue.
More often, early problems only show on blood tests.
That is why routine lab monitoring is essential while taking losartan.

Final Thoughts: Protect Yourself, Not Just Your Blood Pressure

Losartan can be a valuable tool against high blood pressure and kidney damage.
Most people never experience the severe reactions described here.

Still, understanding possible losartan side effects gives you real power.
You can recognize red flags sooner, seek help faster, and discuss options confidently.

Key points to remember:

Never ignore sudden dizziness, swelling, chest pain, or trouble breathing.
Pregnancy and losartan are not a safe combination.
Routine blood tests for kidneys and potassium are not optional extras.
Open conversations with your doctor protect your health.

If you are worried about any reaction, trust that concern.
Call your healthcare provider, describe your symptoms clearly, and ask direct questions.

Your medication should support your life, not quietly threaten it.
By staying informed and attentive, you can use losartan wisely and more safely today. ❤️