Cases/Metabolic Problems and Endocrinology

Low Sodium On Routine Bloods — Free SCA Practice Case

Man with a low sodium on routine bloods

Station Timer

12:00

Golden Minute

Initial Introduction

•Introduce yourself

•Ask an open question — "How can I help you today?"

•Listen — don't interrupt

•Catch early cues

Data Gathering

History, ICE & Diagnosis

Clinical Management

Diagnosis, Plan & Decisions

Safety Net

Follow-up & Close

12:00

Golden Minute

Materials for Candidate

Please review before starting the consultation

Patient Profile

Full Name

Gerald Simmons

Age

72 years

Consultation Type

Telephone

Age

Situation

Telephone Consultation. Booked to discuss blood-test results and his blood-pressure medication.

Reason for Encounter

"Hello Doctor, I'd like to go through my blood results and get back on my usual blood-pressure tablet, please."

Medical Records

●PMH: Hypertension.
●Medications: Ramipril 10 mg OD, amlodipine 10 mg OD, bendroflumethiazide 2.5 mg OD (suspended 2 weeks ago).
●Allergies: NKDA.
●Urgent-care letter (2 weeks ago): 5-day history of muscle cramps, tiredness, generalised weakness; no red flags; observations stable. Sodium 126 mmol/L (moderate hyponatraemia). Advised to suspend bendroflumethiazide; safety-netted; repeat sodium in 2 weeks requested.
●Nurse review (yesterday): BP 177/98 mmHg, pulse 70. Bloods taken.
●Repeat blood results: Sodium 134 mmol/L (now normal); potassium 4.1; urea 5.0; creatinine 78; eGFR 70.

Patient Script

For the friend playing the patient role

Character Overview: You are Gerald, a 72-year-old retired accountant. Two weeks ago you felt unwell with muscle cramps, tiredness, and weakness (you also had a stomach bug with diarrhoea around then). Urgent care found your salt level was low, stopped one of your blood-pressure tablets (bendroflumethiazide), and asked for a repeat test. You feel well now. You are keen to restart that tablet because it controlled your blood pressure well for 15 years, and you are worried your blood pressure is now high — your father died of a stroke. You are reasonable and will accept a clear explanation.

Opening Sentence: "Hi Doctor. I'm calling about my blood results. Two weeks ago I was unwell — cramps and weakness — and the urgent doctor said my salt was low and stopped one of my water tablets. I feel fine now, and I'd really like to get back on it, because it's kept my blood pressure down for years. I'm worried my pressure's up without it."

History if Asked (Data Gathering Phase)

●The episode: "Muscle cramps, tiredness, and weakness for about five days. I couldn't get a GP appointment so I rang 111 and was sent to urgent care. They did bloods and said my sodium was low."
●The diarrhoea (only if asked): "Around the same time I had a stomach bug — diarrhoea for a few days. That cleared up, and the weakness got better, but the cramps hung on, which is why I got seen."
●Now: "I feel completely well now. No cramps, no weakness."
●The medication: "I've taken the bendroflumethiazide for about 15 years — it was added when two tablets weren't controlling my pressure. I stopped it two weeks ago as advised."
●His worry: "I'm anxious my blood pressure's high again without it. My dad had a stroke and died, so it frightens me."

ICE — Ideas, Concerns, Expectations

The patient does not volunteer this information unprompted. These responses surface only when the candidate directly explores his perspective.

●Ideas: Gerald believes the low sodium was caused by his diarrhoea/stomach bug, a one-off, rather than by his long-standing tablet. "I put the low salt down to the tummy bug — a one-off, surely, not the tablet I've taken for years."
●Concerns: He is worried about his raised blood pressure and the risk of a stroke, given his father's death. "My real worry is my blood pressure being high and having a stroke like my father."
●Expectations: He wants his results explained and to restart the bendroflumethiazide that has served him well. "I'd like to get back on the tablet that's worked for me all these years."

If Asked — Medical History and Screen

The patient confirms these details only when directly asked.

●Current symptoms of severe hyponatraemia: "No confusion, no falls, no fits, no drowsiness — I feel well."
●Malignancy/SIADH screen: "No weight loss, no night sweats, no persistent cough, no lumps."
●Medication changes/OTC: "No recent dose changes, and I don't take any over-the-counter tablets or supplements."
●Previous hyponatraemia: "Not that I know of — this is the first time."
●Fluid intake: "Normal — I didn't overdo fluids or anything."
●Social: "Non-smoker, don't drink, healthy diet, I walk with my wife every evening. I live with my wife."

Responses to Management (The Negotiation Phase)

●If the Doctor explains the thiazide caused the low sodium: "So it was the tablet, not just the tummy bug? I hadn't realised a tablet I'd taken for years could suddenly do that." (The tested point is explaining thiazide-induced hyponatraemia clearly.)
●If the Doctor advises against restarting bendroflumethiazide: "But it's controlled my pressure so well for 15 years, and my salt's back to normal now — why can't I just go back on it?" (The tested point is explaining the high recurrence risk and the danger of hyponatraemia, and standing by the recommendation while respecting him.)
●If the Doctor offers an alternative antihypertensive: "So what would I take instead to keep my pressure down?" (The tested point is offering an appropriate alternative and managing the now-uncontrolled BP.)
●If the Doctor addresses his stroke fear: "Given my dad's stroke, how quickly will we get my pressure back under control?"
●If the Doctor arranges follow-up/monitoring: "When would you check my pressure and my salt again?"

Mark Scheme

Domain 1: Data Gathering and Diagnosis

0 / 16 indicators checked+0−0

Positive (0/8)

Negative (0/8)

Domain 2: Clinical Management and Medical Complexity

0 / 18 indicators checked+0−0

Positive (0/9)

Negative (0/9)

Domain 3: Relating to Others

0 / 12 indicators checked+0−0

Positive (0/6)

Negative (0/6)

Clinical Learning Points

Drug-Induced Hyponatraemia

●Many common drugs cause hyponatraemia — most notably thiazide/thiazide-like diuretics, SSRIs/SNRIs, PPIs, carbamazepine, and others. In a patient with low sodium, review the drug chart as a first step.
●Thiazides are a classic cause and the hyponatraemia can occur even after years of stable use, often precipitated by an added stress (e.g. a diarrhoeal illness, as here).

Assess Symptoms, Acuity, and Urgency

●Judge severity by symptoms and acuity: acute or symptomatic hyponatraemia (confusion, seizures, drowsiness, reduced consciousness), or a very low or rapidly falling sodium, is a medical emergency requiring admission.
●Mild, chronic, or asymptomatic hyponatraemia (as here, now resolved) is managed in the community by identifying and removing the cause and monitoring.

Consider the Wider Differential (Including SIADH)

●Beyond drugs, consider hypovolaemia (diarrhoea/vomiting), SIADH, hypothyroidism, adrenal insufficiency, cardiac/hepatic/renal failure, and primary polydipsia. SIADH has important causes including malignancy (notably small-cell lung cancer) — screen for red flags.

Deprescribe the Culprit — Do Not Simply Restart It

●Where a drug has caused hyponatraemia, the safe course is usually to stop it and avoid restarting it, because the recurrence risk is high. Document the culprit to prevent inadvertent re-prescription.

Manage the Consequences of Stopping (Here, Blood Pressure)

●Stopping the culprit may unmask the problem it was treating — here, uncontrolled hypertension. Manage it with an alternative agent: following NICE NG136, and given a thiazide is now unsuitable, options include spironolactone (if potassium ≤4.5, with sodium monitoring), an alpha-blocker (doxazosin), or a beta-blocker (bisoprolol).

Monitoring

●Recheck sodium after any medication change, and recheck blood pressure, with follow-up in 1–2 weeks. Reinforce lifestyle measures.

Safety-Netting

●Safety-net for worsening hyponatraemia (confusion, falls, seizures, drowsiness) and for cardiovascular/stroke symptoms (chest pain, breathlessness, blurred vision, focal weakness, slurred speech) — the latter given his uncontrolled BP.

Common Candidate Mistakes in This Case

●Restarting the culprit: agreeing to restart bendroflumethiazide because the sodium has normalised — the key error.
●Ignoring the uncontrolled blood pressure: failing to manage the raised BP that stopping the thiazide has unmasked.
●Not screening for SIADH/malignancy: attributing the low sodium solely to the drug without considering other causes.
●Misjudging urgency: not recognising when hyponatraemia is an emergency (or over-reacting to a resolved, asymptomatic case).
●Poor communication: overriding his preference without explanation, or failing to address his stroke fear.

Free MRCGP SCA practice case for GP registrars covering Low Sodium On Routine Bloods — Metabolic Problems and Endocrinology. Includes candidate brief, patient script, marking scheme mapped to the RCGP SCA marking domains, and learning points. Built directly from the RCGP curriculum topic stations listed under "How this might be tested in the MRCGP SCA," part of a free library of 79 SCA practice cases for simulated consultation assessment preparation.

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