Type 1 diabetes: ignore the age and look for ketones

Clinical Rounds, the GPAtlas podcast. Endocrinology. 7 minutes. Published 13 September 2026. Free to listen.

Clinical source: our own Ocean article "Type 1 Diabetes & Insulin therapy (T1DM)", last reviewed 31 August 2026.

Transcript

Sarah: Hello, and welcome to GPAtlas Clinical Rounds. I'm Sarah, and today Ben and I are going to be talking about Type 1 diabetes, specifically the challenge of identifying it in the consulting room and the common pitfalls we see when it's mistaken for other conditions.

Ben: Thanks, Sarah. Let's ground this. I had a patient last week, a 34-year-old man, let's call him Mark. He came in feeling lethargic. He mentioned he'd been drinking a lot more water than usual, getting up three or four times a night to use the toilet, and he'd lost about five kilograms over the last month. He was slim, a BMI of about 22. He told me he'd been working hard and thought it was just stress, but he looked pretty washed out. The standard response might be to reach for a metabolic screen, checking a fasting glucose or an H-B-A-1-C, but his presentation, the rapid weight loss, and his age really made my ears prick up. He wasn't acutely unwell, no vomiting or Kussmaul breathing, but he was certainly symptomatic. The trap here, and it's one we see all the time, is to think about Type 2 diabetes because he's a young adult, and maybe just put him on some metformin while we wait for results. But that would be a complete miss. We need to be thinking about insulin deficiency from the second he walks through the door.

Sarah: Absolutely. And that's where the examination and the immediate tests matter. With Mark, you aren't just waiting for the lab. You're doing a finger-prick glucose right there. If that shows something well into the teens, you're not done. You need to check for ketones. I think we’re often guilty of skipping the ketone check in an adult because we associate it so strongly with children, but if you have a symptomatic adult with a high glucose, that urine or blood ketone level is the most vital piece of clinical information you can get in the first ten minutes. If those ketones are up, that is a red flag for diabetic ketoacidosis. Examination-wise, you’re looking for signs of dehydration, tachycardia, checking those lying and standing blood pressures, and also just looking at the patient. Is there evidence of rapid weight loss? I’d also be asking about family history of autoimmune conditions, like thyroid disease or coeliac disease, because we know these conditions cluster. It's also worth asking if he’s had any recent viral illnesses, which can sometimes be the trigger for the autoimmune destruction of the beta cells. I think we also need to be very clear that you cannot rely on an H-B-A-1-C to exclude this. An H-B-A-1-C is a three-month average, and if someone has been losing weight and getting symptomatic over the last four weeks, their H-B-A-1-C might not even be that elevated yet. If your clinical suspicion is high, the H-B-A-1-C is not your safety net. You need to be looking at the current glucose levels, the presence of ketones, and the trajectory of the symptoms. If you see those 4 Ts, thirst, toilet, tiredness, and thinning, that is Type 1 until proven otherwise, regardless of what a blood test says.

Ben: The biggest shift for me on Monday morning is abandoning the idea that Type 1 diabetes is a 'childhood' condition. We have to be comfortable with the fact that it presents across the entire age range, even into the 50s and beyond. Where practice falls short is in the 'anchor and adjust' phase, we see a 40-year-old, we think 'obesity-driven diabetes', we start metformin, and we send them home. If that patient has Type 1, they are essentially being left in an insulin-deficient state. The action required is to stop treating the patient as a generic 'diabetes' diagnosis and start treating them as a potential insulin- deficient patient. If someone has rapid weight loss and ketosis, you do not withhold insulin. You need to get them to the specialist diabetes team that same day. We are not initiating insulin in primary care, that is a specialist-led process, but we are the gatekeepers. If we sit on it, we risk that patient presenting to A and E in full-blown D-K-A. I think we also need to get better at recognizing the atypical cases. If someone has a strong multi-generational family history of diabetes, but they are antibody-negative and not ketotic, we should be thinking about monogenic diabetes, or M-O-D-Y. Those patients don't need insulin; they often need sulfonylureas or, in some cases, no treatment at all. Referring them for genetic testing is the right move there, rather than just putting them on a lifelong insulin regime that they might not actually need. It’s about being precise. Type 1 needs urgent insulin and specialist input, whereas Type 2 is manageable in primary care. If we aren't distinguishing between those, we’re failing the patient. Another area where we fall short is the education piece. We need to be upfront about the fact that this is an autoimmune condition. It's not a lifestyle disease, and we need to move away from the guilt that some patients feel when they get this diagnosis. Finally, remember that for our established Type 1 patients, our role in shared care is critical. We need to be checking those injection sites for lipohypertrophy, reviewing their glucose trends, and ensuring they’ve got their annual foot and eye checks sorted. It’s a longitudinal commitment, not a one-off assessment.

Sarah: The absolute biggest pitfall is the 'anchoring bias', sticking the label of Type 2 on someone just because of their age or their BMI. It is so easy to see a 30-year-old and think 'Type 2' because that's what we see most often in our clinics. We check the H-B-A-1-C, it’s 50, and we think 'metformin and lifestyle advice'. By doing that, we ignore the weight loss and the thirst. If a patient is slim, has lost weight rapidly, or has signs of ketosis, you must not use their BMI or their age as a reason to rule out Type 1. This isn't just about misdiagnosis; it's about life-threatening delay. We are essentially ignoring the fact that the body is failing to produce insulin. Another pitfall is ignoring the sick-day rules for established patients. We see patients who come in with a minor infection, and they think they should stop their insulin because they aren't eating much. We have to be crystal clear: they must keep taking their basal insulin. They might need to adjust their bolus, but they should never, ever stop their basal insulin. We also need to be careful with insulin stacking. If a patient is frustrated by a high blood sugar, they might take an extra bolus dose without waiting for the previous one to work. That’s a recipe for a severe hypoglycaemic episode. We need to educate our patients on the importance of waiting for that 'correction' to kick in before stacking doses. And let's talk about the D-V-L-A rules. It’s not just 'check your sugars'. It’s the '5 to drive' rule. If they are at 5.0 or below, they need carbohydrate. If they are below 4.0, they cannot drive. These are non-negotiable safety rules, and we need to ensure every insulin- using patient knows them inside out. It's the small, repetitive conversations in the routine follow-up that keep our patients safe over the long term.

Sarah: So, to recap: First, never exclude Type 1 diabetes on age or BMI alone; if there is rapid weight loss or ketosis, treat it as Type 1. Second, the diagnosis of Type 1 diabetes is a medical emergency that requires same-day specialist referral for insulin initiation, never delay. And third, for your established Type 1 patients, always reinforce the sick-day rules and the D-V-L-A '5 to drive' safety requirements to prevent complications.

Ben: Thanks, Sarah. That’s all for this week on GPAtlas. We hope this helps you feel more confident in identifying those tricky Type 1 presentations. Join us next time for more clinical rounds.

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