HEART HEALTH
Blood Test for High Blood Pressure UK: Which Tests You Need & What Your Results Actually Mean
Around 14.4 million adults in the UK have high blood pressure, according to the British Heart Foundation. Roughly a third of them do not know it. For many, the first investigation is a blood pressure reading at a GP surgery, a pharmacy, or a home monitor. But what happens after the cuff comes off is equally important.
Blood tests cannot measure blood pressure directly. That requires a sphygmomanometer. What blood tests can do is reveal why your blood pressure is high, whether it has already damaged your kidneys, whether you have hidden diabetes or metabolic syndrome alongside it, and which medication is safest for you to start.
The NICE guideline NG136 recommends blood tests as part of every new hypertension diagnosis. This guide explains what those tests are, what your GP should check, what they often miss, and how to read the results in a way that changes what you do next.
1. Why blood tests matter for hypertension
High blood pressure is not a single disease. It is a sign that your cardiovascular system is under strain, and the causes range from lifestyle factors (salt, weight, alcohol, inactivity) to specific medical conditions (kidney disease, thyroid dysfunction, hyperaldosteronism, diabetes). A blood pressure reading tells you the number. Blood tests tell you why the number is high and what damage it may already be doing.
Without blood tests, your GP is prescribing medication blind. They cannot calculate your QRISK3 10-year cardiovascular risk score (which requires total cholesterol and HDL). They cannot screen for diabetes (which changes blood pressure targets from 140/90 to 130/80). They cannot check kidney function (which determines whether ACE inhibitors or ARBs are safe). And they cannot spot secondary causes that, once treated, may resolve the hypertension entirely.
That is why NICE NG136 recommends blood and urine tests for every person diagnosed with hypertension, before any medication is started.
2. What NICE NG136 recommends
When you are diagnosed with hypertension in the UK, your GP should run the following investigations as part of the initial assessment:
| Test | Why | NICE NG136 section |
|---|---|---|
| eGFR + creatinine | Screen for kidney disease (cause and consequence of hypertension) | 1.3.3 |
| Urine ACR | Detect early kidney damage (microalbuminuria) | 1.3.3 |
| Electrolytes (Na+, K+) | Baseline before starting diuretics/ACE inhibitors; low K+ flags hyperaldosteronism | 1.3.3 |
| HbA1c or fasting glucose | Screen for diabetes (changes BP target to 130/80) | 1.3.3 |
| Full lipid profile | Calculate QRISK3 score (requires total cholesterol + HDL) | 1.3.3 |
| Urine dipstick | Screen for haematuria + proteinuria (kidney damage) | 1.3.3 |
These tests are standard NHS practice. However, they represent a minimum. They do not include thyroid function, inflammatory markers, advanced lipids (ApoB, Lp(a)), or comprehensive metabolic screening — all of which can change the clinical picture significantly.
3. The 8 biomarkers that matter most
Beyond the NICE minimum, these are the biomarkers that give you the fullest picture of what hypertension is doing to your body and why it may be happening.
Kidney function (eGFR + creatinine)
Your kidneys regulate blood pressure by controlling fluid volume and the renin-angiotensin-aldosterone system. Hypertension damages the delicate glomerular capillaries over years, silently reducing filtration capacity. A declining eGFR is the earliest measurable sign of hypertensive nephropathy.
Key threshold: eGFR below 60 mL/min = stage 3 chronic kidney disease. Requires specialist referral and changes medication choice (avoid nephrotoxic NSAIDs, adjust ACE inhibitor dosing).
Urine albumin-to-creatinine ratio (ACR)
Microalbuminuria (ACR 3–30 mg/mmol) is the first sign that high blood pressure is damaging the kidney filtration barrier. It appears before eGFR drops, making it the earliest marker of hypertensive end-organ damage. The NICE CKD guideline (NG203) uses ACR alongside eGFR to stage kidney disease.
HbA1c (glycated haemoglobin)
Diabetes and hypertension are a dangerous combination. Approximately two-thirds of people with type 2 diabetes also have hypertension, and the combination multiplies cardiovascular risk. If your HbA1c is above 42 mmol/mol (pre-diabetes) or above 48 (diabetes), your blood pressure treatment target drops from 140/90 to 130/80 under NICE NG136 and NICE NG28.
Full lipid profile (total cholesterol, HDL, LDL, triglycerides)
Your cholesterol levels combined with blood pressure are the two main inputs for the QRISK3 calculator, which estimates your 10-year cardiovascular risk. A QRISK3 score above 10% triggers statin discussion. Triglycerides above 2.3 mmol/L alongside hypertension suggest metabolic syndrome — a cluster that significantly increases heart attack and stroke risk.
Electrolytes (sodium + potassium)
Potassium is the single most important electrolyte in hypertension. Low potassium (below 3.5 mmol/L) in a hypertensive patient is a red flag for primary hyperaldosteronism (Conn's syndrome), which affects up to 10% of people with resistant hypertension according to Lancet Diabetes & Endocrinology. It is also essential baseline data before starting ACE inhibitors, ARBs, or potassium-sparing diuretics, which raise serum potassium.
Thyroid function (TSH)
Both overactive and underactive thyroid cause hypertension. Hypothyroidism raises diastolic blood pressure (the bottom number) through increased peripheral vascular resistance. Hyperthyroidism raises systolic blood pressure (the top number) through increased cardiac output. A simple TSH test screens for both, yet it is not included in the NICE NG136 minimum panel. This is one of the most commonly missed secondary causes.
hs-CRP (high-sensitivity C-reactive protein)
Chronic low-grade inflammation is both a cause and a consequence of hypertension. Elevated hs-CRP (above 3.0 mg/L) independently predicts cardiovascular events even when blood pressure and cholesterol are controlled. The JUPITER trial (NEJM 2008) demonstrated that targeting elevated hs-CRP with statin therapy reduced cardiovascular events by 44% in people with normal LDL. The NHS does not routinely measure hs-CRP in hypertension workup.
ApoB (apolipoprotein B)
ApoB counts the total number of atherogenic lipoprotein particles in your blood — a more accurate predictor of cardiovascular risk than LDL cholesterol alone. In the context of hypertension, elevated ApoB (above 1.0 g/L) combined with high blood pressure creates a compounding vascular injury: pressure damages the endothelium, and ApoB-rich particles infiltrate the damaged areas. The 2019 ESC/EAS guidelines now recommend ApoB measurement for cardiovascular risk stratification, particularly when triglycerides are elevated.
4. NHS ranges vs optimal cardiovascular ranges
Your GP report will flag results outside the NHS reference range. But “normal” on an NHS report does not mean “optimal for cardiovascular health.” The table below compares the two.
| Marker | NHS “normal” | Optimal for cardiovascular health | Source |
|---|---|---|---|
| eGFR | > 60 mL/min | > 90 mL/min | NICE NG203 |
| HbA1c | 20–42 mmol/mol | 28–34 mmol/mol | NICE NG28 + Diabetes UK |
| Total cholesterol | < 5.0 mmol/L | < 5.0 mmol/L | NICE CG181 |
| LDL cholesterol | < 3.0 mmol/L | < 2.5 mmol/L | ESC/EAS 2019 + Mendelian randomisation |
| HDL cholesterol | > 1.0 (M) / > 1.2 (F) | > 1.3 (M) / > 1.5 (F) | NICE CG181 |
| Triglycerides | < 2.3 mmol/L | < 1.7 mmol/L | ESC/EAS 2019 |
| Potassium | 3.5–5.3 mmol/L | 4.0–5.0 mmol/L | Circulation 2018 |
| TSH | 0.4–4.0 mIU/L | 1.0–2.5 mIU/L | BTF / JCEM 2012 |
| hs-CRP | < 5.0 mg/L | < 1.0 mg/L | AHA / JUPITER trial |
| ApoB | (not routinely measured) | < 1.0 g/L (< 0.8 if high risk) | ESC/EAS 2019 |
The gap between “normal” and “optimal” is where preventive cardiology lives. A total cholesterol of 4.9 is “normal.” Combined with hypertension, it may still contribute to a QRISK3 score that warrants treatment.
5. Secondary hypertension: the treatable 5–10%
Most hypertension is “primary” (essential) — no single identifiable cause. But 5–10% of cases have a specific, treatable cause. Blood tests are how you find it.
| Secondary cause | Blood test clue | Prevalence in hypertension |
|---|---|---|
| Primary hyperaldosteronism (Conn's) | Low potassium (< 3.5) + high sodium | 5–10% of resistant hypertension |
| Chronic kidney disease | eGFR < 60, raised creatinine, proteinuria | ~3% of new diagnoses |
| Hypothyroidism | TSH > 4.0 (especially > 10) | 1–3% |
| Hyperthyroidism | TSH < 0.4 | < 1% |
| Diabetes / metabolic syndrome | HbA1c > 42 + raised triglycerides + low HDL | ~20% comorbid |
| Phaeochromocytoma | Plasma metanephrines (specialist test) | < 0.5% (rare but dangerous) |
| Cushing's syndrome | Elevated cortisol, low DHEA-S | < 1% |
If you are under 40, have resistant hypertension (uncontrolled on 3 medications), or have sudden-onset hypertension, the BHF recommends investigating secondary causes. Your GP may refer you to a specialist, but a comprehensive blood panel can provide the first clues.
6. Five blood test patterns and what they mean
Pattern 1: The metabolic cluster
Markers: Raised HbA1c + raised triglycerides + low HDL + raised hs-CRP
Metabolic syndrome. Hypertension here is one piece of a larger insulin-resistance picture. NICE NG28 applies alongside NG136. Treatment targets tighten. Lifestyle intervention (particularly weight loss and Mediterranean diet) has the largest effect size on this cluster — the Lancet PREDIMED trial showed a 30% reduction in cardiovascular events.
Pattern 2: The kidney damage pattern
Markers: eGFR declining, ACR above 3, potassium creeping up
Hypertensive nephropathy is underway. The kidneys are both cause and victim. ACE inhibitors or ARBs are first-line because they protect the kidneys (NICE NG136 + NG203). Monitoring frequency increases to every 3–6 months. This pattern demands a GP conversation.
Pattern 3: The thyroid mimic
Markers: TSH above 4.0 (especially above 10), fatigue, weight gain, raised diastolic BP
Hypothyroidism causing or worsening hypertension. Levothyroxine replacement may resolve the blood pressure entirely if caught early. NICE NG145 guides thyroid management.
Pattern 4: The aldosterone clue
Markers: Persistently low potassium (< 3.5) despite not taking diuretics
Possible primary hyperaldosteronism. Needs renin:aldosterone ratio testing (specialist). If confirmed, the treatment is specific (spironolactone or surgery for adrenal adenoma) and can be curative. This is the most commonly missed secondary cause.
Pattern 5: The inflammatory driver
Markers: hs-CRP above 3.0 + elevated ApoB + borderline lipids
Vascular inflammation is driving risk independently of cholesterol. The JUPITER trial showed this population benefits from statin therapy even with normal LDL. Lifestyle factors (sleep, visceral fat, gut health, omega-3) have measurable impact on hs-CRP.
7. Blood tests before starting medication
If your GP is about to prescribe an antihypertensive, baseline blood tests are not optional. They are medically necessary.
| Drug class | Essential pre-start blood test | Why |
|---|---|---|
| ACE inhibitor (ramipril, lisinopril) | eGFR + potassium | Can raise potassium and worsen kidney function; baseline needed |
| ARB (losartan, candesartan) | eGFR + potassium | Same mechanism as ACE inhibitors |
| Thiazide diuretic (indapamide) | Electrolytes + eGFR + glucose | Can lower potassium and raise glucose |
| Calcium channel blocker (amlodipine) | Liver function (ALT) | Hepatic metabolism; check baseline liver enzymes |
| Statin (alongside BP meds) | Full lipid profile + ALT | QRISK3 calculation + baseline for monitoring |
NICE NG136 also recommends rechecking kidney function and electrolytes 1–2 weeks after starting or changing an ACE inhibitor or ARB.
8. Ongoing monitoring: how often to test
| Test | If stable + controlled | If starting / changing meds |
|---|---|---|
| eGFR + electrolytes | Annually | 2 weeks, then 3–6 monthly |
| Urine ACR | Annually | At baseline + 6 months |
| HbA1c | Annually | At baseline + 6 months |
| Lipid profile | Annually | At baseline, 3 months post-statin |
| TSH | Every 1–2 years | At baseline; 6-weekly if treated |
| hs-CRP | Every 6–12 months | At baseline, 3 months post-intervention |
The NHS Health Check (offered every 5 years to 40–74 year olds) provides a single snapshot. If you have hypertension, annual comprehensive testing is the minimum standard of care.
9. GP testing vs private: what your GP often misses
| Aspect | GP (NHS) | Helvy |
|---|---|---|
| Markers tested | eGFR, electrolytes, HbA1c, basic lipids (4 markers) | 30–50+ markers including hs-CRP, ApoB, Lp(a), thyroid, vitamins |
| Thyroid screening | Not routine for hypertension | Included in Essential, Performance |
| hs-CRP | Rarely measured unless requested | Included in Heart Health, Performance |
| ApoB + Lp(a) | Not available in most GP surgeries | Included in Heart Health |
| Optimal ranges | Binary (normal / abnormal) | NHS range + optimal cardiovascular range |
| Turnaround | 1–3 weeks (GP appointment + lab processing + follow-up) | 5 working days, results in app |
| Booking | GP appointment required | Home finger-prick, no appointment |
| Doctor review | GP interprets results | GMC-registered doctor reviews every result |
Private testing does not replace your GP. If your blood tests reveal concerning results, take them to your GP. The combination of comprehensive private testing and NHS clinical care gives you the fullest picture.
10. Which Helvy panel covers what
| Marker | Heart £89 | Essential £129 | Performance £149 |
|---|---|---|---|
| Full lipid profile | ✓ | ✓ | ✓ |
| ApoB | ✓ | — | ✓ |
| Lp(a) | ✓ | — | — |
| hs-CRP | ✓ | — | ✓ |
| HbA1c | — | ✓ | ✓ |
| Kidney function | — | ✓ | ✓ |
| Thyroid (TSH) | — | ✓ | ✓ |
| Liver function | — | ✓ | ✓ |
| Iron studies / ferritin | — | ✓ | ✓ |
| Vitamin D | — | ✓ | ✓ |
| Cortisol | — | — | ✓ |
| Testosterone | — | — | ✓ |
For hypertension specifically: the Heart Health panel (£89) covers the advanced cardiovascular markers your GP does not routinely test (ApoB, Lp(a), hs-CRP). The Essential panel (£129) adds kidney function, HbA1c, and thyroid — the secondary cause screening. The Performance panel (£149) covers everything in both.
Not covered: urine ACR (requires a separate urine test), renin/aldosterone ratio (specialist test), plasma metanephrines (specialist test). Ask your GP for these if secondary hypertension is suspected.
11. What to do with your results
Blood test results combined with blood pressure readings create a complete cardiovascular picture. Here are evidence-based interventions ranked by effect size.
| Intervention | BP reduction | Evidence |
|---|---|---|
| Reduce sodium to < 6g/day | −5/3 mmHg | BMJ meta-analysis (He & MacGregor 2002) |
| Increase potassium (fruit, veg, legumes) | −3/2 mmHg | DASH diet trial (NEJM 1997) |
| 30 min aerobic exercise × 5/week | −5–8/4 mmHg | AHA 2017 guidelines |
| Weight loss (per 1 kg lost) | −1/1 mmHg per kg | Cochrane review 2021 |
| Reduce alcohol to ≤ 14 units/week | −4/3 mmHg | Lancet 2018 + NICE NG136 |
| DASH or Mediterranean diet | −6–11/3–6 mmHg | DASH (NEJM 1997) + PREDIMED (Lancet 2018) |
| Omega-3 (2–3g EPA+DHA/day) | −2–4/1–2 mmHg | JACC meta-analysis 2022 |
| Magnesium (300–400 mg/day) | −2/1 mmHg | Hypertension meta-analysis (Zhang et al. 2016) |
Combined lifestyle changes can reduce blood pressure by 10–20 mmHg systolic — equivalent to one or two medications. But these work best when targeted at the specific pattern your blood tests reveal.
12. When to test
- •At diagnosis. Every new hypertension diagnosis needs baseline bloods before medication (NICE NG136).
- •Starting or changing medication. Check kidney function and electrolytes 1–2 weeks after starting ACE inhibitors or ARBs.
- •Annually if stable and controlled. Kidney function, electrolytes, lipids, and HbA1c as a minimum.
- •If blood pressure becomes resistant. Three medications at optimal doses and BP still above target? Investigate secondary causes.
- •Family history of cardiovascular disease. ApoB and Lp(a) testing alongside standard markers gives a more complete inherited risk picture.
Timing: Blood samples for a hypertension workup should ideally be fasting (if lipids and glucose are included). Take medications as normal before the test unless your GP advises otherwise.
13. Frequently asked questions
Can a blood test detect high blood pressure?+
No — blood pressure requires a cuff measurement. Blood tests investigate the causes and consequences of hypertension: kidney damage, diabetes, thyroid disease, electrolyte imbalances, and cardiovascular inflammation.
What blood tests does a GP do for high blood pressure?+
Under NICE NG136: kidney function (eGFR), electrolytes, HbA1c, lipid profile, and urine dipstick. Many GPs also check thyroid function and full blood count. Private testing adds hs-CRP, ApoB, and Lp(a).
How often should I have blood tests with high blood pressure?+
Annually if stable. Every 3–6 months when starting or changing medication. More frequently if you have diabetes or kidney disease alongside hypertension.
Can blood tests show why my blood pressure is high?+
Yes. Blood tests can identify secondary causes including thyroid disease, kidney disease, hyperaldosteronism, and diabetes. Around 5–10% of hypertension cases have a specific treatable cause.
What blood test results are concerning with high blood pressure?+
eGFR below 60, potassium below 3.5, HbA1c above 42, LDL above 3.0, and hs-CRP above 3.0 are all concerning alongside hypertension. Any of these significantly increases cardiovascular risk.
Do I need a blood test before starting blood pressure medication?+
Yes. NICE NG136 recommends baseline kidney function, electrolytes, HbA1c, and lipids before starting antihypertensives. ACE inhibitors and ARBs require potassium and eGFR monitoring.
Can high blood pressure damage my kidneys without symptoms?+
Yes. Hypertensive kidney damage is typically silent until advanced. Annual eGFR and urine ACR testing is the standard of care for detecting it early.
SOURCES
- NICE NG136 — Hypertension in adults: diagnosis and management (2019, updated 2023)
- British Heart Foundation — High blood pressure
- NICE NG203 — Chronic kidney disease: assessment and management
- NICE NG28 — Type 2 diabetes in adults: management
- NICE CG181 — Cardiovascular disease: risk assessment and reduction
- NICE NG145 — Thyroid disease: assessment and management
- ESC/EAS 2019 — Guidelines for the management of dyslipidaemias
- JUPITER trial — Rosuvastatin in persons with elevated hs-CRP (NEJM 2008)
- Lancet Diabetes & Endocrinology — Primary aldosteronism prevalence
- QRISK3 — 10-year cardiovascular risk calculator
Get the full picture of your cardiovascular health
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