Blood Tests Your Doctor Should Order If You Have High Blood Pressure
Hypertension is not just a cardiovascular number — it damages the kidneys, affects electrolytes, and can be caused by secondary conditions like primary aldosteronism or thyroid disease. These blood tests help identify the cause and monitor the consequences.
Upload your blood test PDF and get a free scored health breakdown.
Get My Score →Why Blood Tests Matter in Hypertension
Hypertension affects nearly half of US adults. Most cases are "primary" (essential) hypertension with no single identifiable cause — but up to 10% are "secondary", caused by a treatable underlying condition. Blood tests help screen for these causes, assess end-organ damage, and guide medication choice.
| Test | What to Look For |
|---|---|
| eGFR and creatinine | Kidney damage — both a cause and consequence of hypertension |
| Urine albumin:creatinine ratio | Earliest sign of hypertensive kidney damage |
| Potassium | Low potassium with hypertension suggests primary aldosteronism — important to test before starting diuretics |
| Aldosterone:renin ratio | Screen for primary aldosteronism (a treatable cause) if potassium is low or BP is resistant to treatment |
| TSH | Hypothyroidism and hyperthyroidism both cause hypertension |
| Fasting glucose and HbA1c | Metabolic syndrome and diabetes frequently co-exist with hypertension |
| Full lipid panel | Hypertension + dyslipidaemia = dramatically elevated cardiovascular risk |
| Full electrolytes (sodium, potassium, calcium) | Secondary causes; guide diuretic therapy; monitor ACE inhibitor/ARB effects on potassium |
Blood Tests That Reveal Secondary Hypertension Causes
Primary Aldosteronism: The Most Common Missed Cause
Primary aldosteronism — excess aldosterone production from one or both adrenal glands — accounts for approximately 5–10% of hypertension cases, making it the most common secondary cause. The clue on blood tests is hypokalaemia (low potassium) with hypertension, but potassium can be normal in up to 40% of cases. The aldosterone:renin ratio (ARR) is the recommended screening test. Primary aldosteronism is important to identify because it can be cured with surgery (unilateral adrenal adenoma) or effectively managed with aldosterone antagonists.
Most Hypertension Is Secondary to Insulin Resistance
The most common modifiable metabolic driver of hypertension in the general population is insulin resistance and hyperinsulinaemia — not just high salt intake. Insulin raises blood pressure by increasing sodium renal reabsorption and activating the sympathetic nervous system. Fasting insulin above 10 µIU/mL and a high triglyceride/HDL ratio are the key markers to check alongside standard blood pressure management.
Monitoring Kidney Function on Antihypertensives
ACE inhibitors and angiotensin receptor blockers (ARBs) — first-line drugs for hypertensive patients with diabetes or kidney disease — raise potassium and can transiently increase creatinine in some patients. A creatinine and potassium check 1–2 weeks after starting or increasing the dose is standard practice. A creatinine rise of up to 30% is acceptable and expected — larger rises may indicate renovascular disease and require specialist review.
Medical Disclaimer
This article is for educational purposes only and does not constitute medical advice. Reference ranges, supplement dosages, and nutritional information mentioned are general educational guidance from published research—not personalised recommendations. Do not use this content to self-diagnose or self-treat any condition. Always consult a qualified healthcare provider before making any changes to your health regimen, medications, or supplements.
See exactly where your results stand
Upload your blood test PDF and get a free A–F score across all 6 health domains in seconds.
Analyze My Blood Test →