Key takeaways:
Hydralazine is a medication that’s FDA approved to treat high blood pressure. You’ll typically take it two to four times a day.
The usual daily dose of hydralazine is 100 mg to 200 mg. You may need to take up to 300 mg daily in rare cases if a lower dose doesn’t work well enough.
If you’re living with severe liver or kidney damage, you should use caution when taking hydralazine. Side effects are more likely, and hydralazine may not be a safe option for you.
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Hydralazine is a medication that’s FDA approved to treat hypertension (high blood pressure). It works by relaxing your blood vessels so blood can flow more easily through them. As a result, your blood pressure goes down. Hydralazine isn’t typically a first-choice medication for high blood pressure. But it may be a good option for people who don’t see adequate results with first-choice medications.
Taking the correct hydralazine dosage will help you get the most out of the medication and minimize side effects. Let’s take a look at the typical hydralazine dosages for adults and children. Keep in mind that it's best to follow your prescriber’s instructions, even if they differ from what’s described below.
Good to know: Hydralazine comes as a tablet and an injection. It’s also available in a combination pill called BiDil (isosorbide dinitrate / hydralazine). In this article, we’ll focus on the oral form of hydralazine.
What’s the typical hydralazine dosage for adults?
The typical hydralazine dosage for high blood pressure is 100 mg to 200 mg per day. This daily dose is typically divided into 2 to 4 smaller doses spaced evenly throughout the day. You can take hydralazine with or without food, but it’s best to be consistent with when and how you take it for best results.
In most cases, you’ll start with a lower hydralazine dosage. From there, your prescriber will slowly increase your dosage over time until you find what works best for you. Doses over 300 mg per day aren’t recommended.
The chart below shows a typical dosage schedule for starting hydralazine.
Schedule | Recommended hydralazine dosage |
|---|---|
Days 1-2 (or up to day 4 if needed) | 10 mg four times a day (40 mg/day) |
Days 3-7 | 25 mg four times a day (100 mg/day) |
Days 8 and beyond | 50 mg four times a day (if needed) (200 mg/day) |
What's the typical hydralazine dosage for children?
Hydralazine is not FDA approved for use in children. But it’s sometimes prescribed off-label to treat high blood pressure in younger patients. Instead of the standard dosing used for adults, the hydralazine dose is based on your child’s body weight.
The recommended starting hydralazine dosage for children is 0.75 mg per kg of body weight daily, split into 4 smaller doses taken throughout the day. Depending on how your child responds, their prescriber may slowly raise their dosage over 3 to 4 weeks to a maximum of 7.5 mg per kg of body weight or 200 mg daily.
Are there any dosage adjustments for medical conditions?
Hydralazine is broken down by your liver, then removed from your body through your kidneys. If you’re living with severe liver or kidney damage, you may need a lower hydralazine dosage than described above. That’s because these conditions can cause hydralazine to build up in your body, which could increase the risk of side effects. Your prescriber will adjust your dosage if needed based on your medical history.
Who shouldn’t take hydralazine?
You shouldn’t take hydralazine if you are allergic to it or any of its inactive ingredients.
Taking hydralazine when you have severe kidney damage may increase the risk of drug-induced lupus, a serious potential side effect of hydralazine. Common symptoms of this side effect include joint and muscle pain, fever, and rash. If you’re living with kidney problems, make sure your prescriber is aware of this before you start taking hydralazine.
You shouldn’t take hydralazine if you have a history of certain heart-related health conditions. These include coronary artery disease (including a history of heart attack) or certain types of rheumatic heart disease.
What happens if you miss a dose of hydralazine?
If you miss a dose of hydralazine, take it as soon as you remember. But if it's close to your next scheduled dose, skip the missed dose and just take your next dose at your regular time.
You should never take more hydralazine than prescribed to make up for a missed dose. Taking extra hydralazine may raise your risk of side effects such as fast heart rate, dizziness, and diarrhea.
What should you do if you take too much hydralazine?
If you take too much hydralazine, you may experience extremely low blood pressure, a fast heart rate, or headache. More seriously, you could develop an abnormal heartbeat, have a heart attack, or go into shock.
If you think you may have taken too much hydralazine, contact your prescriber or call Poison Control at 1-800-222-1222 for guidance. But seek emergency care right away if you’re experiencing any of the above symptoms.
How to save on hydralazine
There are ways to save on hydralazine, which is available as a generic medication.
Save with GoodRx: GoodRx can help you save over 50% on the average retail price of hydralazine. With a free GoodRx coupon, the cost of hydralazine 25 mg tablets at certain pharmacies may be as low as $4.86 for a 30-day supply.
Save with GoodRx Companion. You can access discounted prescription medications with a GoodRx Companion subscription. Over 200 medications (including some doses of hydralazine) are available for free, with hundreds more under $10. The program also includes benefits to help you cut your self-pay costs, such as lower prices for online care visits, discounts on dental care, and other health services.
Frequently asked questions
There isn’t a hard rule about taking hydralazine after 6 p.m. But your prescriber may recommend avoiding it too close to bedtime. That’s because hydralazine may cause low blood pressure or a fast heartbeat that can interfere with sleep.
Hydralazine is also often taken along with a diuretic (“water pill”). Diuretics can make you pee more. So taking them too close to bedtime can cause you to wake up more often for nighttime bathroom trips. Talk to your prescriber about the best times to take hydralazine based on your other medications and health needs.
Common hydralazine side effects can include headache, fast heart rate, and decreased appetite. These may improve as your body adjusts to the medication. Rare, but serious side effects of hydralazine include chest pain, mood changes (depression or anxiety), and low blood cell counts.
Let your prescriber know if you notice bothersome side effects after starting hydralazine. And if you’re experiencing life-threatening side effects such as chest pain, seek emergency care.
Oral hydralazine starts to work within 20 to 30 minutes of taking it, but it may take several weeks to find the right hydralazine dosage for your needs. This is because you’ll typically start with a low dose and slowly increase it over time.
There isn’t a hard rule about taking hydralazine after 6 p.m. But your prescriber may recommend avoiding it too close to bedtime. That’s because hydralazine may cause low blood pressure or a fast heartbeat that can interfere with sleep.
Hydralazine is also often taken along with a diuretic (“water pill”). Diuretics can make you pee more. So taking them too close to bedtime can cause you to wake up more often for nighttime bathroom trips. Talk to your prescriber about the best times to take hydralazine based on your other medications and health needs.
Common hydralazine side effects can include headache, fast heart rate, and decreased appetite. These may improve as your body adjusts to the medication. Rare, but serious side effects of hydralazine include chest pain, mood changes (depression or anxiety), and low blood cell counts.
Let your prescriber know if you notice bothersome side effects after starting hydralazine. And if you’re experiencing life-threatening side effects such as chest pain, seek emergency care.
Oral hydralazine starts to work within 20 to 30 minutes of taking it, but it may take several weeks to find the right hydralazine dosage for your needs. This is because you’ll typically start with a low dose and slowly increase it over time.
The bottom line
Hydralazine is a medication that can treat hypertension (high blood pressure). The typical hydralazine dosage for adults is 100 mg to 200 mg daily, divided into 2 to 4 smaller doses taken throughout the day. The hydralazine dosage for children is based on their body weight.
You may need a lower hydralazine dosage if you’re living with kidney or liver problems. Your prescriber can determine the best hydralazine dosage based on your medical history.
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References
Dass, C., et al. (2023). Rheumatic heart disease. StatPearls.
Herman, L. L., et al. (2023). Hydralazine. StatPearls.
Jones, D. W., et al. (2025). 2025 AHA/ACC/AANP/AAPA/ABC/ACCP/ACPM/AGS/AMA/ASPC/NMA/PCNA/SGIM 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 Joint Committee on Clinical Practice Guidelines. Hypertension.
Major Pharmaceuticals. (2025). Hydralazine hydrochloride- hydralazine hydrochloride tablet [package insert].
MedlinePlus. (2017). Hydralazine.
Poison Control. (n.d.). Get Poison Control help online now. National Capital Poison Center.
Saliba, F., et al. (2026). Drug-induced lupus erythematosus. StatPearls.
Scuderi, C. E., et al. (2019). Complex prescribing in chronic kidney disease: Role of the renal pharmacist in kidney supportive care in uncovering hydralazine-related lupus. Journal of Pharmacy Practice and Research.
