Type 1 diabetes: ignore the age and look for ketones

Clinical Rounds, the GPAtlas podcast. Endocrinology. 19 minutes. Published 13 September 2026. Free to listen.

From our Ocean topic Type 1 Diabetes & Insulin therapy (T1DM), reviewed August 2026.

Transcript

Sarah: Hello, and welcome to GPAtlas Clinical Rounds. I'm Sarah, and this is the podcast where we take one thing you'll genuinely see this week and work out what to do with it.

Ben: And I'm Ben. Today it's type one diabetes, and one mistake we keep making with it. We look at the age, we decide it's type two, and nobody checks for ketones.

Sarah: Joanne is fifty-two. She's booked in to go through bloods the nurse took for tiredness, and her glycated haemoglobin, the HbA1c, is seventy-one. She's actually pleased about one thing. She's lost nearly a stone without trying. She's thirsty all the time, she's up in the night to wee, and she's had thrush twice since the summer. She's slim. She's got an underactive thyroid. And I'll be honest, I had the metformin half written and a three- month review in mind before she'd sat down.

Ben: Three things today. Why age and weight must never decide the type of diabetes. Why a ketone check, done there and then, beats waiting for a blood result. And what's ours afterwards, from sick-day rules to the hypos patients stop feeling.

Sarah: So let's start with why I nearly got it wrong. Fifty-two. New diabetes. Raised HbA1c. Every pattern in my head said type two. The idea of type one in a woman her age just didn't arrive. And I don't think I'm unusual there.

Ben: You're not. But our article is blunt about it. Type one makes up somewhere between one in twenty and one in ten of all diabetes. It peaks in puberty and early adulthood. But new- onset type one can happen at any age, so it must never be excluded on age alone. And the slowly evolving adult form, Lada, turns up right across the age range too.

Sarah: So what should have stopped me? She's not twenty. She's not even under fifty, and I know that's on the list. So in my head, the list had already ruled her out. I'd checked one box, found it empty, and stopped reading.

Ben: But that's one feature of five. In an adult with high glucose, our article says suspect type one if there's ketosis, rapid weight loss, onset under fifty, a body mass index under twenty-five, or a personal or family history of autoimmune disease. Joanne has the weight loss, the slim build and the thyroid. That's three, before anyone's dipped anything. And her thrush counts too. Recurrent infection and blurred vision are early clues.

Sarah: And the one age rule I do keep works the other way. Sixty or over, new diabetes, weight loss nobody can explain. Then I'm thinking pancreatic cancer, and arranging an urgent direct-access computed tomography scan. So age changes what I add. It never takes type one off the table.

Ben: Age and BMI never decide the type on their own. Look for weight loss, ketones and autoimmune history.

Sarah: So here's what actually happened. She said the weight loss was the one good bit of her year, and something in me went, hang on. So I dipped her urine and did a finger-prick there in the room. Glucose twenty-three. Urine glucose four plus, and ketones one plus. Small. But there.

Ben: And that's exactly the move. Our article says glucose and ketones, urgently, at the point of suspicion. Not at the next appointment. And then it's simple. If there's ketosis or rapid weight loss, treat it as type one, start the same-day referral, and do not withhold insulin. Joanne had both.

Sarah: Which is the trap I was walking straight into. I was a click away from metformin and a leaflet. Instead I rang the diabetes team, and they saw her that afternoon. Though part of me wondered whether I should just start some insulin myself, there and then.

Ben: Our article names that trap exactly: anchoring on type two in a slim or older adult and reaching for metformin. And on the insulin, no. In type one, insulin isn't started from scratch in primary care. That's different from type two, where we might start basal insulin. The specialist team confirms the diagnosis and starts it. Our job is getting her there today.

Sarah: Ketones at the point of suspicion. Ketosis or rapid weight loss means same-day referral, not metformin.

Ben: Now, her HbA1c was seventy-one, so it fitted. Our article gives the thresholds. A random glucose above eleven point one with symptoms. A fasting glucose of seven or more. Or an HbA1c of forty-eight or more, which confirms diabetes. But it's very clear that you don't rely on HbA1c to diagnose or exclude type one.

Sarah: Because type one can move faster than the test. If Joanne had come in a month earlier, who knows what it would have shown. And I can picture myself telling a thirsty woman who's losing weight that her diabetes test was normal. That's the consultation that frightens me.

Ben: And our article says exactly that. A normal value doesn't exclude rapidly developing disease. And treatment must never be delayed while you wait for it. So when the story's there, it's the finger-prick and the ketones that move you. Not a lab result that comes back on Thursday.

Sarah: A normal HbA1c doesn't rule out type one. Never wait for it.

Sarah: Now picture a different Joanne. Same story, but she's been sick twice this morning, her tummy hurts, and she's breathing deeply, almost sighing. On a busy morning, I think a lot of us hear gastroenteritis and reach for the fluids advice.

Ben: And our article wants a different reflex. Suspect diabetic ketoacidosis, DKA, whenever there's nausea, vomiting, abdominal pain, or that deep sighing breathing, Kussmaul breathing. Add dehydration and drowsiness. And ask about a fruity smell on the breath. In someone with new thirst and weight loss, those symptoms aren't a tummy bug until you've proved it.

Sarah: So I'm examining for it, properly. Mucous membranes. Pulse. Blood pressure lying and standing. I'm smelling her breath, which feels odd, but it's quick. If her mouth's dry, she's tachycardic and her pressure drops when she stands, I'm not sending her home with a leaflet and a sick bowl.

Ben: No. That's emergency admission for intravenous fluids and intravenous insulin. And this is where the ketone check earns its place. Urine ketones two plus or more, or blood ketones three or more, with an illness on top, means admit immediately. Our article doesn't hedge on that.

Sarah: Vomiting, abdominal pain or sighing breaths with high glucose: think DKA and admit.

Sarah: When Joanne came back a fortnight later, already on insulin, she asked two things. Is this forever? And then, before I'd really answered, what about my daughter? She's seven. What am I supposed to be watching for?

Ben: The first one's yes. Our article's patient explanation is plain: the body has stopped making insulin, so it's lifelong insulin. Then for her daughter, it's the four Ts. Thirst. Toilet, so passing lots of urine. Tired. And thinner, meaning weight loss nobody can explain. The trouble is, a lot of children don't arrive with that gradual story at all.

Sarah: How many are we talking? Because my instinct says a child whose first presentation is DKA is unusual. A bad-luck story, not a pattern. The ones I remember all came in with a week of thirst and a worried mum.

Ben: It's a pattern. In audit data here, around a quarter to over a third of children first present in DKA. The highest rates are in the under-fives, who depend on carers to notice. Our article calls delayed recognition the single biggest avoidable harm. So a child with the four Ts gets a finger-prick that day, and a same-day referral to the paediatric diabetes team.

Sarah: Thirst, toilet, tired, thinner. Check a child's glucose that day, because many first arrive in DKA.

Ben: Now the opposite trap, because our article warns about this one too. Not every young person with diabetes has type one. Monogenic diabetes, often called Mody, is commonly mislabelled as type one. And the cost of that label is a lifetime of insulin somebody might not need.

Sarah: So flip Joanne round. Say she's twenty-five, no ketones on the dip, and her mum, her grandad and her brother all have diabetes. Am I still just sending her off to be started on insulin?

Ben: That's the picture. Autosomal dominant, non-ketotic, antibody-negative, with preserved C-peptide and a strong family history across generations. And getting it right changes treatment. Two of the subtypes are sulfonylurea-sensitive, and some of those patients can come off insulin. Another subtype usually needs no treatment at all. So our article says refer atypical cases for genetic testing, rather than committing them to lifelong insulin.

Sarah: And the tests that sort it out sit with the specialists, not with me. For what it's worth, Joanne's team did check her. Two diabetes antibodies came back positive, which is how they separate type one from type two when it's uncertain. So in her case the label was right. It was my first instinct that wasn't.

Ben: Young, no ketones, antibody-negative, strong family history: think Mody and refer for genetic testing.

Sarah: Four months on, Joanne rings on a Monday morning. She's got a chest infection, she's barely eating, and she tells me, quite proudly, that she's skipped her long-acting insulin. No food, so no insulin. She thought she was being careful. And you can see the logic.

Ben: And that's the one belief our article is firmest about. Insulin is replacement, never optional. People with type one are insulin-deficient. Stopping it, even when they're unwell or not eating, rapidly brings on DKA. So the rule is three words. Never stop insulin.

Sarah: So while she was still on the phone, I asked her to check her blood ketones. She had the meter in the kitchen drawer, still in its box. She read it out. Three point two. And that changed the conversation completely.

Ben: It should. Blood ketones three or more, or urine two plus or more, with an intercurrent illness. Our article says admit immediately. And when someone's unwell but managing at home, the sick-day routine is glucose every one to two hours and ketones every three to four. Plus insulin, all the way through.

Sarah: She went in, and she was fine. But afterwards I realised nobody had really taught her the sick-day rules. She'd had the diagnosis four months, and her structured education was still months away. That's a gap we can close.

Ben: Never stop insulin when unwell. Ketones three or more in blood, or two plus in urine, with illness: admit.

Sarah: So at her next review, almost as she was leaving, hand on the door, she said two things. She keeps waking up with headaches. And her partner now spots her hypos before she does. She said it like a joke. And honestly, I nearly laughed along.

Ben: And neither is a joke. Waking with headaches is our article's clue to night-time hypos. And losing the warning symptoms is impaired awareness of hypoglycaemia. That one isn't for watchful waiting. Our article says urgent specialist diabetes referral.

Sarah: And then my mind goes straight to the car. She drives for work. So I'm asking whether she knows the strict driving rules for insulin users. I'm checking what else she takes, over the counter too. And I'm feeling her injection sites for lumps, and watching her technique.

Ben: Good, because our article lists beta-blockers as masking hypo symptoms, and the lumps you're feeling for are lipohypertrophy. Then ask directly about severe episodes, any hypo where someone else had to help. And the emergency answer is simple. Severe hypoglycaemia means intramuscular glucagon or intravenous glucose, and nine nine nine.

Ben: Ask about waking headaches and lost warning signs. Impaired awareness means urgent specialist referral.

Sarah: Which brings me to the long run. After those first weeks, a lot of Joanne's care comes back to us. Repeat prescriptions, reviews, the phone call on a Monday. So what does our article actually hand over?

Ben: Shared care. Repeat prescribing, monitoring, the annual review, and re-referring if control slips. HbA1c every three to six months, against a target you agree with her. Structured education six to twelve months after diagnosis, including carbohydrate counting. And our article says offer continuous glucose monitoring to all adults with type one.

Sarah: And her annual review is a list I can actually run. Eye screening. A full foot risk assessment. Urine albumin to creatinine ratio, renal function and lipids. Thyroid and coeliac screening at diagnosis, then thyroid function every year. And the cardiovascular side, pushed hard: blood pressure, a statin, and stopping smoking.

Ben: And one more thing to ask about: mood. Anxiety, depression, eating disorders, and deliberate insulin omission. Our article's warning sign is recurrent, unexplained DKA, especially in a young woman with a high HbA1c and weight loss. Ask gently, without judgement. It's often concealed, and far more common than the textbooks imply.

Sarah: Which isn't Joanne. But it's the same lesson as the day I met her. What's really going on gets decided by what you ask and what you check. Not by who's sitting in front of you.

Sarah: Annual eyes, feet, kidneys and heart risk. And ask about mood and missed insulin.

Ben: Right, exam corner. A fifty-six-year-old woman with coeliac disease comes in with a month of thirst and a stone of weight loss. Her body mass index is twenty-two. Random glucose is nineteen. She feels otherwise well. What's the most appropriate next step? A. Start metformin and review in three months. B. Check ketones now and refer to the specialist diabetes team the same day. C. Send an HbA1c and decide once it's back. D. Start basal insulin in the practice today.

Ben: B. She's slim, she's losing weight fast, and she has an autoimmune disease. Our article says rapid weight loss or ketosis means treat as type one and refer the same day, whatever her age. A is the tempting one, because fifty-six feels like type two. That's exactly the anchoring our article warns about. C delays treatment for a test that can't exclude type one. And D is wrong too. In type one, insulin is started by the specialist team, not from scratch in primary care.

Sarah: So. Three things for Monday. One. Age and BMI never decide the type. In a slim adult who's losing weight, or has autoimmune disease, type one is on the table. Two. Check glucose and ketones at the point of suspicion, and don't wait for an HbA1c. Ketosis or rapid weight loss means same-day referral. And three. Never stop insulin. Teach the sick-day rules, and ask about the hypos people have stopped feeling.

Sarah: One thing to reflect on, if you're logging this. Think of the last slim adult you diagnosed with type two diabetes. Did anyone check their ketones before the metformin started? Check your local guidance before you act on it. The full transcript and the sources are on the episode page. Ben and I are natural AI voices, and what we've said comes from our reviewed Ocean topic. Check your local guidance before you act on it. See you next week.

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