Hydrochlorothiazide vs. Olmesartan

See how Hydrochlorothiazide and Olmesartan compare on approved uses, dosing, side effects, and cost.

Key Takeaways

  • Hydrochlorothiazide is a low-cost thiazide diuretic that lowers blood pressure by helping the kidneys remove excess salt and water, and it also treats fluid buildup from heart failure or liver disease.

  • Olmesartan is an ARB that relaxes blood vessels by blocking a hormone called angiotensin II, and it is approved only for hypertension, not fluid retention.

  • Both drugs are taken once daily by mouth, but hydrochlorothiazide costs far less out of pocket than olmesartan.

Hydrochlorothiazide vs. Olmesartan Drug Summary

Hydrochlorothiazide

Hydrochlorothiazide is a thiazide diuretic that lowers blood pressure and reduces fluid buildup by helping the kidneys excrete extra salt and water. It treats hypertension as well as edema from heart failure, cirrhosis, kidney problems, or steroid and estrogen use. It is taken as an oral tablet or capsule once a day.

Olmesartan

Olmesartan is an angiotensin II receptor blocker (ARB) that relaxes blood vessels by blocking a hormone that narrows them, lowering blood pressure. It is approved to treat hypertension in adults and children six and older, used alone or with other blood pressure medicines. It comes as an oral tablet taken once a day.

Hydrochlorothiazide vs. Olmesartan Side Effects

Hydrochlorothiazide

Most common
Weakness (not specified)
Hypotension (not specified)
Hypokalemia (not specified)
Hyperglycemia (not specified)

Olmesartan

Most common
Dizziness (up to 3%)
Headache (>1%)
Back pain (>1%)
Diarrhea (>1%)

Hydrochlorothiazide vs. Olmesartan Dosage

Hydrochlorothiazide

Dosage
Dosage Table
STAGE DOSE WHEN
Starting dose 25 mg once daily At the start
Maximum dose 25-100 mg once daily If needed
Dose changes 2 increases As tolerated

Olmesartan

Dosage
Dosage Table
STAGE DOSE WHEN
Starting dose 10 mg once daily At the start
Maximum dose 40 mg once daily Week 3 onward
Dose changes 2 increases As tolerated

Hydrochlorothiazide vs. Olmesartan Indications

Hydrochlorothiazide

Hydrochlorothiazide is FDA-approved for high blood pressure, either alone or combined with other blood pressure drugs. It also treats fluid retention linked to heart failure, liver cirrhosis, kidney disease, and long-term steroid or estrogen use.

  • Treats high blood pressure

  • Treats edema from heart failure

  • Treats edema from liver cirrhosis

  • Treats edema from kidney disease

Olmesartan

Olmesartan is FDA-approved to treat high blood pressure in adults and children six years and older. It can be used alone or combined with other antihypertensive medicines, but it is not recommended as the first therapy in patients 75 or older or with liver problems.

  • Treats high blood pressure in adults

  • Treats high blood pressure in children 6+

  • Can be combined with other blood pressure drugs

  • Not for first-line use over age 75

Hydrochlorothiazide vs. Olmesartan Pros and Cons

Hydrochlorothiazide

Hydrochlorothiazide has decades of safety data and works for both blood pressure and fluid retention, making it useful beyond hypertension alone. It is inexpensive and widely covered by insurance, though it can cause meaningful electrolyte shifts that need monitoring.

Pros

  • Also treats edema, not just high blood pressure

  • Roughly $4 to $35 per month without insurance, far less than olmesartan

  • Decades of clinical use and well-established safety data

  • Can be combined with potassium-sparing diuretics to offset electrolyte loss

Cons

  • Can cause hypokalemia, hyponatremia, and other electrolyte problems needing blood tests

  • Raises blood sugar and uric acid levels

  • Long-term use linked to higher risk of non-melanoma skin cancer

  • Not recommended during pregnancy

Olmesartan

Olmesartan targets a single pathway in blood pressure regulation and generally causes fewer electrolyte disturbances than a diuretic. It carries a boxed warning against use in pregnancy and needs caution in people prone to high potassium or low blood volume.

Pros

  • Fewer electrolyte disturbances than a diuretic

  • Approved for children 6 years and older

  • Doses above 40 mg show no added benefit, simplifying dosing

  • Once-daily dosing with no advantage to splitting doses

Cons

  • Roughly $115 to $205 per month without insurance, much pricier than hydrochlorothiazide

  • Boxed warning for fetal toxicity in pregnancy

  • Risk of hyperkalemia, especially with kidney issues

  • Sprue-like enteropathy (severe diarrhea and weight loss) reported with delayed onset

Common Symptoms and Related Diseases You Can Explore

Explore a range of common symptoms the Doctronic Symptom Checker can help you understand.