Hydrochlorothiazide: Uses, Side Effects, and How to Take It
Hydrochlorothiazide, often called a water pill, is a diuretic that helps the kidneys remove extra salt and water from the body. It is used to treat high blood pressure and fluid retention, including swelling caused by certain heart, kidney, or liver conditions. It can also affect potassium and other electrolyte levels, so periodic monitoring may be needed.
Hydrochlorothiazide can help lower blood pressure and reduce swelling, but it may cause dizziness, dehydration, and changes in potassium or sodium levels. Take it only as prescribed and ask your doctor or pharmacist about your personal risks, especially if you take other medicines.
Key facts at a glance
- ATC
- C03AA03
- Generic
- Hydrochlorothiazide
- Class
- thiazide-diuretic
- Brands
- Microzide
- Availability
- rx
- Pregnancy
- B
- Lactation
- caution
- Half-life (h)
- 10
- Onset (min)
- 120
- Duration (h)
- 24
- Routes
- oral
- Forms
- tablet
- Regions
- CN, US, EU, JP
- Monitoring
- electrolytes, blood-pressure, blood-glucose
This page is for informational purposes only.
Do not use this information to diagnose yourself or to replace a physician's advice. Always consult a qualified healthcare provider before starting, stopping, or changing any medication. If you believe you are experiencing a medical emergency, call your local emergency number immediately.
Dosage and administration
- Usual dose
- 500mg twice daily
- Maximum
- consult physician
- Frequency
- every 12 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 250mg twice daily
- Maximum
- consult physician
- Frequency
- every 12 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 400mg daily
- Maximum
- consult physician
- Frequency
- once daily
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
Overdose information
Special Populations
10 groupspregnancy
first trimesteravoid if possible
avoid use during pregnancy unless benefits outweigh risks
regular fetal monitoring
Use of this medication in this population requires careful consideration of risks and benefits.
pregnancy
second trimesteravoid
discontinue use, thiazides may cause fetal and neonatal complications
fetal growth monitoring, check amniotic fluid levels
Use of this medication in this population requires careful consideration of risks and benefits.
pregnancy
third trimesteravoid
avoid near delivery, may cause adverse effects in newborn
monitor fetal heart rate, assess for neonatal complications
Use of this medication in this population requires careful consideration of risks and benefits.
lactation
breastfeedinguse with caution
if needed, use lowest effective dose, monitor infant for side effects
monitor infant for signs of dehydration, electrolyte imbalance
Use with caution and monitor for adverse effects.
pediatric_age
children adolescentsdose based on weight
use in children 6 months and older for edema, monitor electrolytes
monitor weight, electrolytes, renal function
geriatric
elderlystart with low dose
use lowest effective dose, monitor for orthostatic hypotension
regular monitoring of electrolytes, renal function, blood pressure
Use with caution and monitor for adverse effects.
renal_impairment
mild moderatemay need dose reduction
monitor renal function, may be less effective in severe impairment
monitor serum creatinine, BUN, electrolytes
Use with caution and monitor for adverse effects.
renal_impairment
severeuse with extreme caution
generally not recommended, may be ineffective
frequent monitoring of renal function and electrolytes
Use with caution and monitor for adverse effects.
hepatic_impairment
mild moderateno major adjustment needed
use with caution, monitor electrolytes
monitor liver function tests, electrolytes
Use with caution and monitor for adverse effects.
alcohol_users
chronic alcohol useavoid or limit
may exacerbate electrolyte depletion, monitor closely
monitor electrolytes, liver function
Use with caution and monitor for adverse effects.
Statistics and clinical data
Commonly prescribed since
General prescribing information
Drug class
Drug class information
Common uses
Common therapeutic uses
Mechanism of action
Pharmacological mechanism
Contraindications
Conditions and patient states where this medication should be avoided or used with caution.
Do not use (1)
Known allergy to this medication or its components
Use caution (1)
Consult healthcare provider for benefits vs risks assessment
Official drug label
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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed July 22, 2026. · Read our editorial policy