The GNL FAQ shelf

GLP-1 receptor agonists (such as liraglutide and semaglutide) are medicines that mimic a gut hormone released after eating. They slow gastric emptying, reduce appetite, and suppress glucagon. Dual GLP-1/GIP agonists (such as tirzepatide) act on two gut-hormone pathways at once. Both are licensed for type 2 diabetes and obesity, not for type 1 diabetes. Grade D

No. No GLP-1 receptor agonist or GLP-1/GIP agonist is licensed for type 1 diabetes anywhere. Use in T1D is off-label, specialist-led, and individual. The FDA declined to approve liraglutide for T1D after the ADJUNCT trials, on the basis of efficacy and safety together. Grade A

Randomised controlled trials show GLP-1 receptor agonists can reduce total daily insulin by roughly 10 to 25 percent in adults with type 1 diabetes, alongside modest improvements in time in range. The effect varies considerably between individuals. Grade A

Tirzepatide evidence in T1D is currently limited to a single-centre observational cohort of 26 people (Akturk and Shah, 2025). It suggests a larger insulin reduction, around 30 percent, but observational data cannot be compared directly to randomised trial outcomes, and no randomised trial in T1D has yet reported. Phase 3 trials are ongoing. Grade B

Across randomised trials in adults with T1D, GLP-1 receptor agonists produce clinically meaningful weight loss, commonly in the range of 4 to 10 kg at six months. The amount varies with agent, dose, and individual response. Grade A

The 2025 ADJUST-T1D trial combined semaglutide with automated insulin delivery and reported a composite outcome (time in range above 70 percent, time below range under 4 percent, and at least 5 percent weight loss) met by 36 percent of the semaglutide group versus 0 percent of the control group. It is one of the strongest signals to date for the AID-plus-GLP-1 combination. Grade A

GLP-1 and GIP therapies can raise the risk of ketosis in type 1 diabetes, particularly if insulin is reduced too far or too fast. Euglycaemic ketosis (ketones rising while glucose looks normal) was seen in around 8 percent of participants in one crossover study. No DKA occurred in modern AID-era trials, but the ketone signal is real and ketone monitoring remains standard of care. Grade B

Symptomatic hypoglycaemia can occur if insulin is not reduced proactively as the medicine takes effect. This is why dose changes are specialist-led and gradual. Grade A

Gastrointestinal effects (nausea, reduced appetite, occasionally vomiting) are the most common and are usually dose-related and most prominent early. Emerging signals around lean-mass loss and bone are being studied and are not yet settled. Grade B

No. There are no Phase 3 trials of these agents in children or adolescents with type 1 diabetes. ISPAD 2024 flags this as an urgent gap. This FAQ concerns adults only. Grade D

The strongest evidence is in adults with type 1 diabetes and obesity or marked insulin resistance. Decisions are individual and specialist-led, weighing potential benefits against the ketosis, hypoglycaemia, and tolerability considerations above. Grade D

Whether adjunct therapy fits individual goals, how insulin would be adjusted, how ketones would be monitored, and what to watch for in the first weeks are all reasonable topics. The right plan is the one built with the diabetes care team. Grade D

Skin problems in people using CGM and insulin pumps almost always come from a mismatch between load and recovery. Devices increase load on the skin through adhesive contact, occlusion, sweat trapping, friction, and repeated micro-trauma from insertions. Managing skin is not about achieving perfect skin; it is about managing that load by choosing better sites, rotating intelligently, preparing the skin properly, removing gently, and building recovery time into the rotation cycle.

• Pick flatter sites, avoid rub zones, and rotate properly.
• Prep means clean plus fully dry; most adhesion issues are moisture and friction issues.
• Use barriers only when needed; too much coverage can create new problems.
• Remove low and slow with oil or adhesive remover to avoid skin tears.
• Recover on purpose: moisturise and rest sites, and avoid re-using a site just because it looks acceptable.

• Irritation or rash: often adhesive allergy or irritant contact dermatitis, sweat trapping, or repeated low-grade trauma from movement.
• Dry or itchy skin and eczema: commonly occurs when the skin barrier does not recover adequately between wears.
• Lipohypertrophy and lipoatrophy: tissue changes from repeated insulin delivery and overuse of the same zones. Lipohypertrophy causes hardened fatty deposits; lipoatrophy causes hollowing.
• Scars, wounds, and skin tears: most often caused by rapid removal technique rather than slow, oil-assisted removal.
• Infection: warm, red, painful, spreading, or discharging areas need prompt review.

Site placement determines a significant proportion of skin outcomes. Sites too close to joints, waistbands, scars, or high-friction areas tend to create irritation. Sites used too repeatedly cause tissue breakdown and, for pump users, increase lipohypertrophy risk.

• Prefer flat, fatty zones: upper arms, buttocks, thighs, and flanks.
• Avoid areas that bend or rub, such as waistbands and bony creases.
• Rotate deliberately: use 6 to 10 zones and give each at least a week of rest.
• Keep at least 1 to 2 inches away from previous sites or current insulin delivery areas.

Preparation does not need to take long; it needs to be consistent.

• Clean with oil-free soap and water. Avoid alcohol-based prep wipes if you react to them.
• Dry thoroughly. Damp skin and steamy bathrooms are the two most common causes of adhesion failure.
• For people who sweat heavily: apply a thin layer of solid, unscented antiperspirant to the site, leave for around 10 minutes, then wipe off completely before applying the device.

For people prone to reactions, introduce one variable at a time and observe the effect: barrier wipes (for example Cavilon or Skin Tac) to protect the skin surface, barrier films placed under the device (for example IV3000 or Tegaderm) for sensitive skin, or fluticasone spray, sometimes used off-label as a clinician-guided strategy, applied and allowed to dry completely before the device goes on.

Where possible, avoid extra tape to limit total skin coverage under occlusion. But sometimes the device adhesive does not hold well enough, and sometimes it holds too well.

• Over-patches can help when adhesion is poor (for example RockaDex, GrifGrips, Simpatch).
• When using additional tape, picture-frame around the edges rather than full coverage where possible.
• Elastic wraps (for example Coban) or kinesiology tape can be useful for sport and high-sweat situations.

Most skin tears occur from pulling the sensor or patch upward and away from the skin, rather than folding it back on itself slowly.

• Use baby oil, olive oil, or dedicated adhesive removers (for example Lift Plus, Uni-Solve, or TacAway) to loosen the adhesive before removal.
• Start at a corner. Push the skin down gently with one hand and slowly fold the tape back over itself, not up and away.
• Once removed, clean the site and apply a moisturiser.

Whether the skin feels fine or slightly irritated after removing a device, what happens next matters.

• Use a rich, unscented moisturiser daily, especially on sites currently resting.
• Leave used sites alone for at least a week before reusing them.
• Watch for infection signs: heat, pus, spreading redness, or escalating pain. Escalate to a clinician earlier rather than later if these appear.

The DVLA requirement is to be at or above 5.0 mmol/L (90 mg/dL) before starting the engine. At 4.0 to 4.9 mmol/L (72 to 88 mg/dL), the guidance is to have a snack, re-check if needed, and then drive once above 5.0 mmol/L (90 mg/dL). Below 4.0 mmol/L (72 mg/dL), a hypo must be treated, glucose confirmed above 5.0 mmol/L (90 mg/dL), and a wait of 45 minutes observed before driving. The 45-minute wait exists because cognitive and reaction-time recovery lags behind glucose recovery after neuroglycopenia.

After treating a hypo and confirming glucose is above 5.0 mmol/L (90 mg/dL), the DVLA requirement is to wait 45 minutes before driving. Experimental and driving-review evidence shows that attention, processing speed, and reaction time can remain impaired for 30 to 45 minutes after glucose normalises following a hypoglycaemic episode. The rule is designed to cover this worst-case recovery window. Grade B

Group 1 covers cars and motorcycles (vehicles up to 3.5 tonnes with up to 8 passengers). Group 2 covers HGVs, buses, and minibuses (vehicles over 3.5 tonnes or with more than 8 passengers). Group 2 carries stricter medical and monitoring requirements.

For Group 1, both CGM or flash glucose monitoring and finger-prick testing are accepted for pre-drive and in-journey checks. For Group 2, finger-prick testing is required for the legally required checks; CGM is not currently accepted for the legal checks for Group 2 drivers.

The requirement is to check before driving and at least every two hours while driving. One way to think about it: every check expires after two hours on a long journey. Keeping a backup meter and strips in the car is recommended, and the date and time on the meter should be correct, because legal and forensic review may depend on it.

A severe hypoglycaemic episode is one requiring assistance from another person to recover. For Group 1 licence holders, more than one severe episode while awake in the preceding 12 months requires stopping driving and notifying the DVLA. For Group 2 licence holders, any severe episode in the preceding 12 months requires stopping driving and notifying the DVLA. The responsibility for notification sits with the driver: clinicians advise, but legal notification is the driver’s duty.

Pull over safely and treat immediately. Confirm glucose is above 5.0 mmol/L (90 mg/dL). Wait 45 minutes before driving again. The same principle applies after an overnight low: confirm above 5.0 mmol/L (90 mg/dL), then wait 45 minutes before driving.

The DVLA does not define an upper glucose limit for driving. Acute hyperglycaemia at high levels (for example glucose clamped at around 16 to 17 mmol/L, roughly 290 to 305 mg/dL) has been shown to slow information processing and working memory and worsen mood in experimental settings, primarily in type 2 diabetes populations, so how this translates to type 1 diabetes varies. The operative principle is symptomatic: if hyperglycaemia is producing symptoms such as blurred vision, poor concentration, or fatigue, driving is not the right next step regardless of the number. Grade C

International consensus defines below 3.9 mmol/L (70 mg/dL) as Level 1, an alert value, and below 3.0 mmol/L (54 mg/dL) as clinically significant hypoglycaemia. A useful teaching point: 4 mmol/L (72 mg/dL) is an alert value, not a clinical definition of hypoglycaemia, and many people do not experience symptoms at 4 mmol/L (72 mg/dL) unless glucose is actively falling. The DVLA bar for licensing is loss of awareness, not the alert threshold itself. Grade A

Clinicians advise. Legal responsibility for notification and the decision to drive sits with the driver under DVLA rules.

The body treats alcohol as a toxin and the liver prioritises clearing it. During this process, the liver suppresses glycogen release and gluconeogenesis, the two main mechanisms that prevent or correct hypoglycaemia. Glucagon becomes far less effective at stimulating liver glucose output. The practical result is that overnight hypoglycaemia risk increases considerably after drinking. A commonly used rule of thumb is that one unit of alcohol corresponds to approximately one hour of impaired liver glucose output, though individual responses vary. Grade B

Three mechanisms align at the same time: basal insulin continues lowering glucose, the liver stops releasing glucose, and glucagon becomes ineffective. This combination can cause delayed hypoglycaemia, overnight unawareness, and in rare cases coma. Harm reduction is the appropriate framework here, not abstinence-only guidance.

Alcohol disrupts REM sleep, which is required for memory consolidation. When REM collapses, memories from the night do not form normally. This can explain apparent blackouts even without extreme intoxication; wearables with sleep tracking often show near-zero REM after heavy alcohol intake.

With repeated exposure, alcohol dehydrogenase ramps up, meaning alcohol is cleared more rapidly. The same intake produces less intoxication, so more is consumed to feel the same effect. Long-term intake also depletes B vitamins, particularly thiamine, which is one reason careful tapering matters when heavy alcohol use stops.

Three pillars tend to underpin safer drinking in T1D: continuous glucose monitoring, a hypo plan (fast-acting carbohydrate accessible and understood by companions), and a buddy system where at least one person in the group understands T1D and how to respond to a hypo. Additional strategies many people find helpful include eating before drinking, hydrating throughout the evening, monitoring glucose more frequently than usual, planning for next-morning lows, and using a medical ID or CGM sharing with a trusted contact.

A systematic review (Tetzschner 2018, drawing on 13 primary studies and 13 international guidelines) found no consensus per-unit insulin reduction figure in the published literature. The GNL Alcohol Explorer encodes graduated bands as an educational synthesis on a strong underlying evidence base, framed as starting points for exploration, never as instructions. Grade D synthesis on a Grade A/B base

• MDI (multiple daily injections): on a population-average basis at the user’s TDD anchor, a long-acting (basal) reduction of roughly 25 to 75 percent on the evening of drinking, combined with reducing or omitting the bolus for carbohydrate-containing drinks, is the band the GNL Explorer surfaces to limit overnight low risk. The right band varies considerably between individuals.
• Pump therapy: on a population-average basis at the user’s TDD anchor, a temporary basal reduction of roughly 25 to 75 percent run overnight is the band the Explorer surfaces. Your pump’s basal profile, set with your care team, is the authoritative reference.
• AID systems: Activity Mode (or the system’s equivalent reduced-target mode) tends to be used and left on overnight, with awareness that the system may still attempt corrections based on sensor glucose. Discuss any sustained change with your diabetes care team.

These bands are starting points for exploration with CGM feedback and the diabetes care team, not universal instructions.

Glucagon works largely through the liver. If the liver is busy clearing alcohol and glycogen stores are limited, glucagon may be less reliable than expected after heavier drinking. In a severe hypo after heavier drinking, the first action is to call an ambulance and the second is to attempt glucagon.

The evidence base for recreational drugs in type 1 diabetes is very limited and is not based on randomised trials. Different substances can affect appetite, hydration, glucose awareness, sleep, and the ability to recognise or respond to a hypo in different ways, and they can interact with alcohol. The same harm-reduction principles apply: keep CGM running, keep fast-acting carbohydrate accessible, and make sure at least one trusted person knows you have T1D and how to respond to a hypo. Specific substance and interaction questions are best worked through with a diabetes care team without judgement. Grade D [VERIFY-MA]

Open conversation tends to be more protective than silence. Parents can help by practising safety strategies in advance, providing a supportive environment to learn, discussing risks honestly, and making sure communication plans are in place. For clinicians, asking about alcohol and nightlife without judgement, avoiding projecting personal values, and treating harm reduction as a clinical priority are the principles that most benefit this conversation. A difficult night is more useful as a learning point than as evidence of failure.