18 Hydroxycorticosterone (18-OHB)
It measures an adrenal steroid linked to aldosterone pathways and hypertension workups, with ordering and clear results support through Vitals Vault/Quest.
This panel bundles multiple biomarker tests in one order—your report explains how results fit together.
18-hydroxycorticosterone (often shortened to 18-OHB) is a steroid hormone your adrenal glands make as part of the pathway that leads toward aldosterone, one of the body’s main salt-and-water regulators.
This is not a routine “annual physical” lab. It is usually ordered when you and your clinician are trying to explain patterns like high blood pressure that is hard to control, low renin findings, unusual potassium results, or a suspected adrenal cause of hypertension.
Because 18-OHB sits in a specific part of adrenal steroid production, the value is most useful when it is interpreted alongside related hormones (especially aldosterone and renin) and with attention to how the sample was collected.
Do I need a 18 Hydroxycorticosterone test?
You may be a good candidate for an 18-hydroxycorticosterone test if your blood pressure pattern suggests an adrenal driver rather than “essential” hypertension. This includes resistant hypertension (still high despite multiple medications), hypertension that starts at a young age, or hypertension paired with low potassium (or potassium that drops easily when you start a diuretic).
This test is also sometimes used when your aldosterone/renin testing is abnormal or borderline and your care team is trying to subtype a low-renin hypertension picture. In that setting, 18-OHB can add context about where aldosterone synthesis may be “running hot” and whether an adrenal steroid pathway is shifted.
You usually do not need this test for general fatigue, weight changes, or stress symptoms alone. It is a targeted endocrine lab that works best as part of a clinician-directed evaluation, not as a stand-alone self-diagnosis tool.
If you are already under endocrine or hypertension specialty care, ask whether 18-OHB would change next steps (repeat aldosterone/renin under standardized conditions, confirmatory testing, imaging, or medication adjustments).
This is a laboratory-developed test performed in a CLIA-certified lab; results support medical decision-making but do not diagnose a condition by themselves.
Lab testing
Order 18 Hydroxycorticosterone testing and schedule your draw at a Quest location.
Schedule online, results typically within about a week
Clear reporting and optional clinician context
HSA/FSA eligible where applicable
Get this test with Vitals Vault
If you are working through a complex blood pressure or adrenal question, Vitals Vault lets you order 18-hydroxycorticosterone without needing to chase paperwork. You can schedule your draw through the Quest network and keep your results organized in one place.
Because collection conditions can meaningfully affect adrenal and renin-angiotensin markers, PocketMD can help you review your result in context—what else to check, what to repeat, and what questions to bring to your clinician—especially if your first set of hypertension labs was done under non-standard conditions.
If your result points toward a broader cardiometabolic retest (kidney function, electrolytes, glucose, lipids) or a deeper adrenal workup, you can coordinate follow-up labs through Vitals Vault and track trends over time.
- Order online and draw at a Quest location
- PocketMD helps you interpret results alongside related hormones
- Designed for repeat testing and trend tracking when your plan changes
Key benefits of 18 Hydroxycorticosterone testing
- Adds pathway-level context when aldosterone and renin results are abnormal, borderline, or hard to reconcile with your blood pressure pattern.
- Helps your clinician evaluate adrenal steroid production beyond a single aldosterone number, especially in low-renin hypertension workups.
- Can support subtyping discussions in suspected primary aldosteronism and related adrenal causes of hypertension.
- Provides another data point when potassium findings (low or easily lowered) suggest mineralocorticoid excess.
- May help explain why blood pressure remains high despite multiple medications, prompting more targeted next-step testing.
- Improves interpretation when reviewed together with aldosterone, renin (or plasma renin activity), and electrolytes rather than in isolation.
- Makes it easier to organize specialty-oriented labs and revisit the question after medication or posture/collection standardization changes.
What is 18 Hydroxycorticosterone?
18-hydroxycorticosterone (18-OHB) is a steroid hormone made in your adrenal cortex. It is closely related to corticosterone and sits in the biochemical neighborhood of aldosterone production.
Aldosterone is the hormone that tells your kidneys to retain sodium and water and excrete potassium. When aldosterone activity is inappropriately high for your body’s needs, your blood pressure can rise and potassium can fall. 18-OHB is not the same as aldosterone, but it can reflect how active certain adrenal steroid steps are, which is why it sometimes appears in specialized hypertension and endocrine evaluations.
Because adrenal steroid output can shift with posture, salt intake, time of day, stress, and medications, the meaning of 18-OHB depends heavily on the testing context and on companion labs.
Where it fits in a hypertension workup
Most people are first screened for adrenal-driven hypertension with aldosterone and renin (often reported as an aldosterone-to-renin ratio). If that screen is abnormal or unclear, additional steroid markers like 18-OHB may be used to add detail about adrenal steroid production patterns and to help guide what to do next.
Why collection conditions matter
Renin-angiotensin and adrenal steroid markers can change with body position (lying down vs sitting/standing), sodium intake, and many blood pressure medications. If your draw was not done under standardized conditions, your clinician may recommend repeating the broader set of labs rather than over-interpreting a single value.
What do my 18 Hydroxycorticosterone results mean?
Low 18-hydroxycorticosterone levels
A low 18-OHB result is often not concerning on its own, especially if aldosterone, renin, electrolytes, and blood pressure do not suggest mineralocorticoid excess. In some contexts, a lower value can be seen when overall adrenal steroid production is reduced or when the pathway toward aldosterone is less active. The most practical next step is usually to confirm that companion markers (aldosterone, renin, potassium, sodium) match the clinical picture rather than treating the 18-OHB number in isolation.
In-range (expected) 18-hydroxycorticosterone levels
An in-range 18-OHB result generally suggests that this part of adrenal steroid production is not markedly shifted. If you are being evaluated for primary aldosteronism, an in-range 18-OHB does not rule it out, because aldosterone regulation can be abnormal even when related intermediates are not striking. Your clinician will typically weigh this result alongside aldosterone/renin findings, potassium, and how your blood pressure behaves on and off certain medications.
High 18-hydroxycorticosterone levels
A high 18-OHB result can indicate increased activity in adrenal steroid pathways related to aldosterone production, which may fit with a low-renin or mineralocorticoid-excess pattern of hypertension. It does not diagnose a specific disorder by itself, but it can strengthen the case for a more structured endocrine evaluation when paired with abnormal aldosterone/renin results or low potassium. If your value is high, it is common to review collection conditions and medications first, and then consider repeat standardized testing or additional confirmatory steps recommended by your clinician.
Factors that influence 18-hydroxycorticosterone
Posture and timing can matter: some adrenal and renin-angiotensin markers differ when you are supine versus seated/standing, and they can vary across the day. Sodium intake and hydration status can shift the broader system that regulates aldosterone-related hormones. Many blood pressure medications (including diuretics, ACE inhibitors, ARBs, beta blockers, and mineralocorticoid receptor antagonists) can change aldosterone/renin patterns and may indirectly affect how your 18-OHB result should be interpreted. Acute illness, significant stress, and lab-to-lab method differences can also contribute, so your report’s reference range and the testing conditions are part of the result.
What’s included
- 18 Hydroxycorticosterone
Frequently Asked Questions
What does an 18-hydroxycorticosterone test measure?
It measures 18-hydroxycorticosterone (18-OHB), an adrenal steroid related to the pathway that produces aldosterone. It is mainly used in specialized evaluations of low-renin or suspected adrenal-related hypertension.
Is 18-hydroxycorticosterone the same as aldosterone?
No. Aldosterone is the main mineralocorticoid hormone that directly affects sodium retention and potassium excretion. 18-OHB is a related steroid that can provide additional context about adrenal steroid production, but it does not replace aldosterone and renin testing.
Do I need to fast for an 18-hydroxycorticosterone blood test?
Fasting is not always required for 18-OHB itself, but your clinician may prefer morning testing and may pair it with other labs that do require fasting. The more important issue is standardizing posture, timing, salt intake, and medication handling when you are also evaluating aldosterone and renin.
Can blood pressure medications affect 18-OHB results?
They can affect the overall aldosterone-renin system, which changes how adrenal steroid results should be interpreted. Diuretics, ACE inhibitors, ARBs, beta blockers, and mineralocorticoid receptor antagonists are common examples. Do not stop medications on your own; ask your prescribing clinician whether any adjustments are needed before testing.
What does a high 18-hydroxycorticosterone level mean for hypertension?
A high value can fit with increased adrenal steroid activity in pathways related to aldosterone, especially when paired with low renin, high aldosterone, or low potassium. It is not diagnostic by itself, so it is typically used as one piece of a broader workup and may prompt repeat standardized testing or confirmatory evaluation.
What other tests are usually interpreted with 18-OHB?
Common companion tests include aldosterone, renin (or plasma renin activity), the aldosterone-to-renin ratio when available, electrolytes (especially potassium), and kidney function (creatinine/eGFR). Depending on your situation, your clinician may also consider cortisol or other adrenal steroid measurements.