Hydrochlorothiazide · thiazide diuretic

Care that knows when HCTZ is the right add-on, and when it's the wrong one.

HCTZ pairs well with an ACE inhibitor or ARB but raises uric acid and can drop potassium. Clara reads your labs, gout history, and meds, then drafts the right plan.

Get started How it works

My BP is 138/88 on lisinopril 20 mg. My doctor mentioned adding HCTZ. Safe?

Clara

HCTZ is a standard ACE add-on, but your 2022 gout attack and uric acid of 7.2 make it a poor choice (HCTZ can trigger flares). I'd draft amlodipine 5 mg as the add-on instead. Sending to our physician.

Clara

If our physician prefers HCTZ despite the gout, I'll draft an allopurinol plan and the follow-up BMP at 2 weeks.

How it works

HCTZ prescribed from your labs, not a checklist.

Connect your chart

Clara auto-syncs your records from 150,000+ doctors' offices, hospitals, labs, and wearable devices. Gout history, A1c, potassium, sodium, creatinine, uric acid — all read. Free.

Clara reasons across your full context

Clara screens for thiazide gotchas (gout, diabetes, low sodium, low potassium, sulfa allergy, NSAID use, skin-cancer history) and drafts the right dose, or a better alternative. A licensed physician reviews and signs off.

Follow-up labs, on a clock

Clara drafts a BMP at 2 to 4 weeks after starting or escalating HCTZ to catch potassium or sodium drift, and watches it without a new visit.

How Clara uses HCTZ

Starting doses, the combinations that work, and when to pick something else.

Rx · Starting

HCTZ 12.5 mg daily

Most BP benefit shows up at 12.5 to 25 mg once daily; higher doses add more metabolic side effects than BP lowering¹.

12.5–25 mg

Usual daily range¹

Rx · Combination

HCTZ + lisinopril (Zestoretic)

A widely used single-pill combination. The ACE inhibitor offsets thiazide-induced potassium drop and the two work on complementary mechanisms.

Single-pill combination

Rx · Combination

HCTZ + losartan (Hyzaar)

Preferred when ACE-inhibitor cough is a problem. Same potassium-sparing logic as the ACE combo, with ARB benefits in diabetic nephropathy³.

Single-pill combination

Rx · Alternative

Chlorthalidone

Longer-acting thiazide-like diuretic. ALLHAT was built on chlorthalidone, and some evidence favors it over HCTZ for CV outcomes². Clara drafts chlorthalidone when your chart supports it.

Alternative when indicated

Safety · Contra

Gout, severe kidney disease, sulfa allergy

HCTZ can precipitate gout, is less effective at eGFR <30, and is a sulfonamide (cross-reactivity is rare but noted). Clara flags these from your chart and drafts an alternative before the order is called in¹.

3 flags

Auto-checked every time

Safety · Skin

Skin cancer watch

The FDA updated the HCTZ label to note increased risk of non-melanoma skin cancer with long-term use; Clara flags if you have prior skin-cancer history and recommends sun protection and dermatology follow-up¹.

Flagged

Cross-checked against chart

Why Clara

A thiazide that knows your gout history and your uric acid. Can your old doctor read your entire chart every time?

	Clara	GoodRx Care	Circle Medical	Your doctor
24/7 AI clinical chat with full-chart reasoning	✓ Unlimited	Per-visit only	Visit-based	✗
Auto-screens gout, A1c, eGFR, skin-cancer before Rx	✓ Every time	Manual at visit	Manual at visit	Dependent on time
Cost to start	Free (connect records + chat)	$49 per BP refill visit	$179 first visit self-pay	$150+ copay
Paid plans	$25/mo membership, HSA/FSA eligible	No membership, $49/visit ($19 w/ GoodRx Gold)	No membership, $120 follow-up self-pay	Per-visit copay
Prescription fills	FDA-approved generic, may be covered by your insurance	Sent to your pharmacy	Sent to your pharmacy	Sent to your pharmacy
Follow-up electrolytes at 2–4 weeks	✓ Drafted automatically	Separate visit	Ordered at visit	Copay applies
Full primary care in one membership	✓	Single-visit refill	✓	✓

The AI difference

The oldest BP drug, handled with the newest reasoning.

Thiazides are the cheapest and most-studied antihypertensives in the world. They also have a handful of drug-specific gotchas that do not fit in a 15-minute visit. Clara handles them automatically, every time.

Gout, diabetes, low sodium, auto-flagged

Your chart has a 2022 gout flare, an A1c of 6.2, or a baseline sodium of 134. Clara pulls it up and drafts a non-thiazide alternative before you end up in the ER with a flare or a hyponatremia admission.

Potassium drift, watched

Clara drafts a follow-up BMP at 2 to 4 weeks and auto-reads it. If potassium dips below 3.5, Clara flags — often a switch to an ACE/ARB-combined pill that evens it back out, without an extra visit.

Chlorthalidone vs HCTZ, from your data

Some patients do better on chlorthalidone based on ALLHAT-era evidence and their chart specifics. Clara flags the choice with the reasoning already laid out, rather than defaulting to whatever is in the EMR drop-down.

Common questions

HCTZ questions patients ask.

How is Clara different from a single refill visit?

A refill visit hands you a prescription and sends you home. Clara keeps reading — your BMP, your home BP, and every other condition on your chart. If potassium drifts, sodium drops, or uric acid climbs on the next lab draw, Clara flags it and drafts a response against your full record. That is a category of continuous reasoning a one-off visit cannot do.

Why does HCTZ cause low potassium?

Thiazides increase sodium delivery to the distal nephron, which drives potassium excretion in exchange. Clara drafts a follow-up BMP at 2 to 4 weeks and pairs HCTZ with an ACE inhibitor or ARB (which raises potassium slightly) to balance it out. If potassium still drifts, Clara drafts a potassium-sparing add-on or a swap back to a non-thiazide.

Is 12.5 mg enough, or do I need 25 mg?

Most of the BP benefit is at 12.5 to 25 mg. Doses above 25 mg add more metabolic side effects (hypokalemia, hyponatremia, hyperuricemia) without much additional BP drop¹. Clara rarely drafts HCTZ >25 mg; the decision is individualized to your response and chart.

Is chlorthalidone a better thiazide?

There is ongoing debate. Chlorthalidone has a longer half-life and was the thiazide used in ALLHAT, one of the largest BP trials ever run². HCTZ is much more commonly prescribed in the U.S. The 2020 DCP trial comparing them head-to-head in veterans found no CV difference but more side effects on chlorthalidone⁴. Clara reads your chart and drafts whichever fits better.

Does HCTZ really raise skin cancer risk?

The FDA added language about an increased risk of non-melanoma skin cancer with long-term HCTZ use based on observational data¹. Absolute risk for most patients is low, but Clara flags the label warning if you have a prior skin-cancer history and recommends sun protection plus dermatology follow-up.

Is Clara a real medical practice?

Yes. Clara is licensed in all 50 states and operates through affiliated professional corporations. A licensed physician reviews and signs off on every prescription and lab order Clara's AI drafts. Clara's AI handles intake, monitoring, and follow-up; physicians provide medical oversight.

What does Clara cost, and can I use insurance?

Connecting records and chatting with Clara is free. Paid plans start at $25/month for medical advice, prescriptions, and lab orders. All plans are HSA/FSA eligible. Clara's membership is cash-pay and not billed through insurance. Prescriptions Clara writes go to your pharmacy and may be covered by your insurance, and ad-hoc lab orders may be covered by your insurance, depending on your plan.

Can I use Clara for other health issues too?

Yes. One membership covers full primary care. Many patients on HCTZ are also managing high cholesterol or type 2 diabetes; Clara's AI connects the dots across all of them. Wearables like Oura and Garmin feed resting heart rate and HRV straight into the BP context.