Aldosterone is a hormone that helps control blood pressure, blood volume, sodium, and potassium. It is made by the adrenal glands, which sit above the kidneys. An aldosterone blood test is most often ordered when a clinician is looking for a hormone-related cause of high blood pressure, low potassium, dizziness with low blood pressure, salt loss, or unexplained electrolyte changes. The result is not read like a simple “high or low” number. Aldosterone changes with posture, salt intake, hydration, time of day, menstrual cycle, pregnancy, kidney blood flow, and several common blood pressure medicines. For that reason, the normal range on the lab report matters more than any single internet range. The result is also more useful when it is compared with renin, potassium, sodium, bicarbonate, kidney function, and the circumstances of the blood draw.
- Aldosterone mainly helps the kidneys retain sodium and water while releasing potassium into urine.
- A common adult blood reference range is about 3–16 ng/dL after lying down and about 4–31 ng/dL after being upright, but lab ranges vary.
- High aldosterone with low renin can suggest primary aldosteronism, a treatable cause of high blood pressure.
- Low aldosterone can contribute to low blood pressure, salt wasting, high potassium, dehydration, or adrenal insufficiency patterns.
- Preparation affects results: posture, salt intake, potassium level, time of day, and medications should be handled exactly as the ordering clinician or lab instructs.
- Aldosterone is usually interpreted with renin, not by itself, because the aldosterone-renin pattern shows whether the hormone response is appropriate.
Table of Contents
- What the Aldosterone Blood Test Measures
- Aldosterone Normal Range and Units
- Why Aldosterone Results Change So Much
- What High Aldosterone Can Mean
- What Low Aldosterone Can Mean
- Aldosterone-Renin Ratio and Result Patterns
- How to Prepare for the Test
- Follow-Up After an Abnormal Result
What the Aldosterone Blood Test Measures
An aldosterone blood test measures the amount of aldosterone circulating in the blood at the time the sample is drawn. Aldosterone belongs to a group of hormones called mineralocorticoids. Its main job is to help the body manage sodium, potassium, water, and blood pressure.
Aldosterone works mostly in the kidneys. When aldosterone rises, the kidneys tend to hold on to more sodium. Water follows sodium, so blood volume and blood pressure can rise. At the same time, the kidneys release more potassium into urine. This is why excess aldosterone can cause high blood pressure and low potassium, while too little aldosterone can cause low blood pressure, salt loss, dehydration, and high potassium.
Aldosterone is part of the renin-angiotensin-aldosterone system, often shortened to RAAS. When the kidneys sense low blood flow, low sodium delivery, or reduced effective blood volume, they release renin. Renin starts a hormone chain that can lead to higher aldosterone. This response is useful when the body needs to preserve fluid, such as after dehydration. It becomes a problem when aldosterone stays high when the body does not need it.
Clinicians commonly order aldosterone testing when a person has:
- High blood pressure that starts young, is hard to control, or needs several medicines
- High blood pressure with low potassium
- An adrenal nodule found on imaging
- A family history of early high blood pressure or primary aldosteronism
- Unexplained high potassium, low sodium, dehydration, or low blood pressure
- Possible adrenal insufficiency or aldosterone deficiency
- A need to compare aldosterone with renin in a hormone blood pressure workup
Aldosterone is closely tied to other kidney and electrolyte tests. If potassium is abnormal, a clinician may compare aldosterone with potassium and creatinine patterns to judge whether the kidneys, medicines, or hormone signals may be contributing. If sodium or fluid balance is the main concern, aldosterone may be interpreted with sodium and osmolality results.
Aldosterone testing is not usually a general screening test for healthy people. It is most useful when the clinical pattern already suggests a blood pressure hormone issue, an adrenal problem, or an electrolyte imbalance that needs a more specific explanation.
Aldosterone Normal Range and Units
There is no single normal aldosterone range that applies to every person in every testing situation. The result depends heavily on posture, sodium intake, time of day, potassium level, pregnancy status, and assay method. A value that looks normal after lying down may be too low after being upright. A value that looks high on a low-salt diet may be expected for that situation.
Many U.S. labs report aldosterone in ng/dL. Some reports use pmol/L. To convert approximately, 1 ng/dL of aldosterone is about 27.7 pmol/L.
| Collection situation | Example reference range | How to read it |
|---|---|---|
| Supine, after lying down | About 3–16 ng/dL | A lower range is expected because standing-related RAAS stimulation is reduced. |
| Upright, seated or standing | About 4–31 ng/dL | Aldosterone usually rises after a person has been upright. |
| Random or non-standardized draw | Lab-specific | Interpretation is harder unless posture, time, salt intake, and medications are known. |
| Pregnancy | Often higher than nonpregnant ranges | Renin and aldosterone normally rise during pregnancy, so pregnancy-specific interpretation is needed. |
| Children and infants | Age-specific | Newborns and infants can have higher values; pediatric ranges should be used. |
The lab’s own reference interval should be treated as the primary range. Aldosterone assays are not perfectly interchangeable. Two labs may use different sample types, calibration methods, and reporting intervals. A result of 18 ng/dL, for example, might be mildly above one supine range but acceptable for an upright sample in another lab.
Aldosterone also has diagnostic cutoffs, and those are different from normal reference ranges. In primary aldosteronism screening, clinicians may look for an aldosterone value that is not just “in range” or “out of range,” but inappropriately high compared with a suppressed renin level. Some screening approaches require aldosterone to be above a minimum level, often around 10–15 ng/dL, before calling an aldosterone-renin ratio meaningful. Those thresholds vary by lab, renin method, and clinical protocol.
For a reader trying to understand one result, the most useful first questions are:
- Was the sample drawn after lying down or after being upright?
- Was it collected in the morning?
- Was potassium low, normal, or high?
- Was sodium intake typical, restricted, or high?
- Was renin measured at the same time?
- Were any interfering medicines continued or paused?
- Does the lab report give a posture-specific reference range?
Aldosterone is a hormone result, not a stand-alone diagnosis. A number just outside the reference range may be less meaningful than a “normal” number that is inappropriate for the person’s renin, blood pressure, potassium, and preparation conditions.
Why Aldosterone Results Change So Much
Aldosterone can change from one day to the next, and sometimes from one hour to the next. That variability is normal physiology. The test becomes useful when the collection conditions are controlled well enough to tell whether the body’s response is appropriate.
Posture has a large effect. When a person stands or sits upright, gravity shifts some blood volume downward. The kidneys may respond by increasing renin, which can raise aldosterone. After lying down, this stimulus is lower. This is why a report may show different ranges for “supine” and “upright” samples.
Salt intake also changes aldosterone. Low sodium intake tends to raise renin and aldosterone because the body is trying to conserve salt. High sodium intake tends to suppress them. A person who has been eating very little salt may have a higher aldosterone level without having an adrenal tumor. A person who has been eating a very high-salt diet may have lower aldosterone than expected.
Potassium matters too. Higher potassium can stimulate aldosterone release. Low potassium can suppress aldosterone secretion and may make primary aldosteronism screening less reliable. This is why clinicians often correct low potassium before testing when it is safe and appropriate.
Time of day affects the result. Morning collection is often preferred because hormone patterns are more standardized earlier in the day. Sleep, stress, exercise, dehydration, illness, and recent fluid intake can also influence results.
Medicines are a major source of confusion. Several blood pressure and kidney medicines change renin, aldosterone, or both. Diuretics can raise renin and aldosterone by reducing effective blood volume. ACE inhibitors and ARBs can raise renin and may lower aldosterone. Beta blockers can suppress renin and may create a falsely high aldosterone-renin ratio. Spironolactone and eplerenone directly block mineralocorticoid effects and can strongly interfere with testing. Nonsteroidal anti-inflammatory drugs, clonidine, oral contraceptives, licorice products, heparin, and some antidepressants can also affect interpretation.
Kidney function changes the picture. The kidneys help regulate renin release, potassium handling, sodium balance, and acid-base balance. When kidney function is reduced, potassium and renin patterns may not behave as expected. A clinician may compare aldosterone with creatinine and eGFR to decide whether an abnormal result fits a kidney-related pattern, a hormone-related pattern, or both.
Because aldosterone responds to so many signals, repeat testing is common. A repeat result collected under clear instructions may be more helpful than a single random value.
What High Aldosterone Can Mean
High aldosterone means the measured value is above the expected range for the collection conditions, or higher than it should be compared with renin. The meaning depends on whether renin is low, normal, or high.
High aldosterone with low renin is the classic screening pattern for primary aldosteronism. In primary aldosteronism, the adrenal glands make too much aldosterone even when the body is not asking for it. This can happen because of an aldosterone-producing adrenal adenoma, overactivity in both adrenal glands, or less commonly inherited forms or adrenal cancer. The common clinical pattern is high blood pressure, suppressed renin, and sometimes low potassium.
Low potassium is an important clue, but its absence does not rule out primary aldosteronism. Many people with primary aldosteronism have normal potassium, especially earlier in the condition or while taking medicines that raise potassium. This is one reason aldosterone-renin testing is considered in selected people with resistant hypertension even when potassium is normal.
High aldosterone with high renin suggests secondary aldosteronism. In this pattern, aldosterone is usually responding to a signal from the kidneys or circulation. Possible causes include dehydration, blood loss, diuretic use, low salt intake, kidney artery narrowing, heart failure, cirrhosis with fluid shifts, nephrotic syndrome, or other states where the kidneys sense low effective blood volume.
A high aldosterone result can show up with:
- High blood pressure that is difficult to control
- Low potassium, muscle cramps, weakness, or palpitations
- Increased thirst or urination in some people
- Metabolic alkalosis, often reflected by higher bicarbonate or CO2 on a chemistry panel
- Suppressed renin when aldosterone secretion is autonomous
- Elevated renin when aldosterone is responding to reduced kidney perfusion or fluid volume
A high result should not be treated as proof of an adrenal tumor. Imaging alone can also mislead, because adrenal nodules are common with age and may not be the source of hormone excess. When primary aldosteronism is suspected, clinicians usually confirm the biochemical pattern first, then decide whether adrenal imaging or adrenal venous sampling is needed.
A related guide to high aldosterone blood test results can be helpful when the result is clearly above the lab range, but the renin and potassium pattern still determines the next step.
High aldosterone is medically important because treatable hormone-driven blood pressure can strain the heart, blood vessels, kidneys, and brain over time. Treatment may include targeted blood pressure medicine, mineralocorticoid receptor blockers such as spironolactone or eplerenone, sodium guidance, or surgery when a unilateral aldosterone-producing adrenal source is confirmed.
What Low Aldosterone Can Mean
Low aldosterone means the level is below the expected range for the collection conditions, or too low for the body’s needs. As with high results, renin is essential for interpretation.
Low aldosterone with high renin suggests the body is trying to stimulate aldosterone, but the adrenal glands are not responding enough. This can happen in primary adrenal insufficiency, some congenital adrenal enzyme disorders, autoimmune adrenal disease, adrenal damage, or rare aldosterone synthesis problems. When aldosterone deficiency is significant, the kidneys may waste sodium and retain potassium.
Low aldosterone with low renin suggests the signal from the kidneys is reduced. This pattern can occur in hyporeninemic hypoaldosteronism, which is more common in people with diabetes, chronic kidney disease, older age, or certain medication effects. It can contribute to high potassium, especially when combined with ACE inhibitors, ARBs, NSAIDs, potassium supplements, trimethoprim, or potassium-sparing diuretics.
Low aldosterone can be associated with:
- High potassium
- Low sodium, especially in adrenal insufficiency or severe salt loss
- Low blood pressure or dizziness when standing
- Salt craving
- Dehydration or volume depletion
- Fatigue, weakness, nausea, or weight loss when cortisol deficiency is also present
- Metabolic acidosis, sometimes reflected by low bicarbonate or CO2
The combination of low aldosterone and high potassium deserves careful review because potassium can affect heart rhythm when it becomes severely abnormal. A clinician may compare aldosterone with a broader electrolyte panel, kidney function, medication list, and blood pressure pattern.
Low aldosterone does not always mean adrenal failure. Aldosterone may be low after high salt intake, while taking certain medicines, or when testing was not done under the intended conditions. It may also be lower in people whose renin is suppressed for reasons unrelated to adrenal gland damage.
When cortisol deficiency is suspected along with low aldosterone, clinicians may order cortisol, ACTH, adrenal antibody testing, or stimulation testing. Aldosterone is only one part of adrenal function. The adrenal glands also make cortisol and adrenal androgens, and the urgency of follow-up depends on the full clinical picture.
A related guide to low aldosterone blood test results can help separate low-renin and high-renin patterns, but symptoms and potassium level should guide how quickly the result is addressed.
Aldosterone-Renin Ratio and Result Patterns
The aldosterone-renin ratio, often called ARR, compares aldosterone with renin. It is mainly used to screen for primary aldosteronism in people with certain high blood pressure patterns. The ratio helps answer whether aldosterone is high despite renin being suppressed.
Aldosterone alone can be misleading. A person who is dehydrated may have high aldosterone because renin is high. That is an appropriate response. A person with primary aldosteronism may have aldosterone that is only mildly elevated, but renin may be very low. That mismatch can produce a high ARR.
Renin may be reported as plasma renin activity, often in ng/mL/hour, or as direct renin concentration, often in mU/L or similar units. These methods are not interchangeable. ARR cutoffs depend on which renin test was used and which units appear on the report. This is why a ratio should be interpreted with the lab’s own cutoff.
| Aldosterone | Renin | Common interpretation pattern |
|---|---|---|
| High or inappropriately normal | Low | Possible primary aldosteronism, especially with high blood pressure or low potassium. |
| High | High | Possible secondary aldosteronism from dehydration, diuretics, kidney artery narrowing, or low effective blood volume. |
| Low | High | Possible adrenal underproduction, aldosterone synthesis problem, or primary adrenal insufficiency pattern. |
| Low | Low | Possible hyporeninemic hypoaldosteronism, medication effect, high salt intake, or kidney-related renin suppression. |
| Normal | Normal | May be appropriate, but interpretation still depends on posture, salt intake, potassium, and symptoms. |
ARR screening is not perfect. False positives and false negatives happen. A high ratio may occur if renin is artificially suppressed by beta blockers or some central blood pressure medicines. A false-negative screen can happen if renin is raised by diuretics, ACE inhibitors, ARBs, low salt intake, or mineralocorticoid receptor blockers. Low potassium can also reduce aldosterone and hide a primary aldosteronism pattern.
When ARR suggests primary aldosteronism, clinicians may repeat testing, adjust medications if safe, correct potassium, and confirm the diagnosis with a suppression test. Confirmation may involve saline infusion, oral salt loading, fludrocortisone suppression, or captopril challenge, depending on the patient and local practice.
A separate renin blood test guide can help explain why renin units and methods matter so much. In real clinical use, aldosterone and renin are a pair. The ratio is strongest when the sample was collected under a protocol designed for the question being asked.
How to Prepare for the Test
Preparation should follow the ordering clinician’s instructions because the purpose of testing changes the protocol. Screening for primary aldosteronism, evaluating low blood pressure, and checking adrenal replacement therapy may each require different handling.
Many aldosterone tests are collected in the morning. The lab or clinician may ask whether the sample should be drawn after lying down, after sitting, or after being upright for a set period. Some protocols use at least 2 hours upright before collection; others specify a seated sample after several minutes of rest. The posture should be written down because it affects the reference range.
Do not change salt intake unless instructed. A sudden low-salt diet can raise aldosterone and renin. A sudden high-salt diet can suppress them. For many evaluations, clinicians want the person to eat their usual diet. For some confirmatory tests, sodium intake is deliberately controlled.
Potassium should be reviewed before testing. If potassium is low, aldosterone may appear lower than expected. In primary aldosteronism screening, low potassium can weaken the signal that clinicians are trying to detect. Potassium replacement may be recommended before testing, but this should be done with medical guidance.
Medication review is one of the most important parts of preparation. Common medicines that can affect interpretation include:
- Spironolactone, eplerenone, amiloride, and triamterene
- Thiazide and loop diuretics
- ACE inhibitors and ARBs
- Direct renin inhibitors
- Beta blockers
- Clonidine and similar central agents
- NSAIDs
- Heparin
- Estrogen-containing hormone therapy or oral contraceptives
- Licorice products, including some herbal or candy forms
Some medicines may need to be continued because stopping them would be unsafe. Others may be changed temporarily under supervision. People with severe hypertension, heart disease, kidney disease, or high potassium should not stop blood pressure or kidney medicines on their own.
The blood draw itself is usually simple. Blood is taken from a vein, and the sample is handled according to the lab’s requirements. Some aldosterone tests use serum; others use plasma. Renin samples can be more sensitive to handling, temperature, and timing. If aldosterone and renin are drawn together, the clinic or lab should know the protocol before the blood is collected.
Bring the medication list, supplement list, recent diet changes, and posture details to the appointment. A technically “normal” result can be hard to interpret if no one knows whether the person was supine, seated, fasting, salt-restricted, dehydrated, or taking an interfering medicine.
Follow-Up After an Abnormal Result
Follow-up depends on the pattern, the severity of symptoms, and related blood test results. Mild aldosterone abnormalities often lead to repeat testing under better-controlled conditions. More concerning patterns, such as high blood pressure with suppressed renin and low potassium, usually deserve a more directed evaluation.
When high aldosterone and low renin suggest primary aldosteronism, the next step may include repeating aldosterone and renin, checking potassium and kidney function, reviewing medicines, and performing a confirmatory suppression test. If primary aldosteronism is confirmed, adrenal CT may be ordered. If surgery is being considered, adrenal venous sampling may be needed to determine whether aldosterone excess comes from one adrenal gland or both.
If the source is one adrenal gland, surgery can sometimes cure or greatly improve the hormone problem. If both adrenal glands are overproducing aldosterone, treatment usually involves mineralocorticoid receptor blockers and blood pressure management rather than removing both glands. Treatment often improves potassium and can reduce the number or dose of blood pressure medicines, although long-standing hypertension may not disappear completely.
When low aldosterone is the concern, follow-up may include renin, cortisol, ACTH, sodium, potassium, bicarbonate, creatinine, glucose, and sometimes adrenal antibody testing. If adrenal insufficiency is possible, clinicians may evaluate cortisol production urgently, especially when symptoms include weight loss, vomiting, severe fatigue, fainting, dehydration, low blood pressure, or darkening of the skin.
An aldosterone result should be addressed promptly if it comes with severe blood pressure elevation, chest pain, shortness of breath, fainting, confusion, severe weakness, paralysis-like symptoms, persistent vomiting, or a very abnormal potassium result. These features can signal a situation that needs urgent care rather than routine outpatient follow-up.
Many people with abnormal aldosterone results feel frustrated because the first test does not give a simple answer. That is common. Aldosterone testing is pattern-based. A clinician is usually trying to decide whether the hormone response is appropriate for the body’s salt, fluid, kidney, and blood pressure signals. The answer often comes from several pieces: aldosterone, renin, ARR, potassium, sodium, bicarbonate, kidney function, medications, posture, and symptoms.
For people being monitored over time, it is helpful to keep copies of reports. Record the collection time, posture, major medication changes, potassium level, and blood pressure readings around the test date. Trends collected under similar conditions are easier to interpret than isolated values collected under different circumstances.
References
- The Management of Primary Aldosteronism: Case Detection, Diagnosis, and Treatment: An Endocrine Society Clinical Practice Guideline 2016 (Guideline)
- Screening Rates for Primary Aldosteronism Among Individuals With Hypertension Plus Hypokalemia: A Population-Based Retrospective Cohort Study 2022 (Study)
- The Unrecognized Prevalence of Primary Aldosteronism: A Cross-sectional Study 2020 (Study)
- Adrenal insufficiency 2021 (Review)
- Conn Syndrome 2025 (Review)
- Physiology, Renin Angiotensin System 2025 (Review)
Disclaimer
Aldosterone results should be interpreted by a qualified clinician using the lab’s own reference range, the collection conditions, medications, renin result, blood pressure pattern, and electrolyte results. Do not stop blood pressure, kidney, potassium, steroid, or hormone medicines before aldosterone testing unless the prescribing clinician gives specific instructions. Seek urgent medical care for severe weakness, fainting, confusion, chest pain, shortness of breath, severe dehydration, very high blood pressure, or a dangerously abnormal potassium result.
