This guide is for information only and is not a substitute for individual medical advice. Always work with your endocrinologist or diabetes care team before making changes to medication, insulin dosing, or exercise protocols. Diabetes management is individual — what works for one cyclist may be wrong for another, and the specifics of your condition, medication, and physiology must drive the decisions you make.
Diabetes does not stop you riding. It does not stop you racing. It does not stop you pinning a number on at a Gran Fondo and suffering up every climb alongside riders who have no idea about the metabolic management happening inside your jersey pocket. Phil Southerland founded Team Novo Nordisk — an entire professional cycling team where every rider has type 1 diabetes — and that team races at Continental level on the international calendar. The proof that diabetes and serious cycling are compatible is not theoretical. It is racing on television.
But here is what most cycling advice gets wrong. The standard fuelling guides, the standard training plans, the standard "eat 60 grams of carbs per hour" advice — all of it assumes a functioning pancreas and normal insulin regulation. If you have type 1 diabetes, your body cannot modulate insulin during exercise. If you have type 2, your body's insulin response is impaired in ways that change the entire fuelling equation. Generic cycling nutrition advice is not just incomplete for you. Parts of it are actively dangerous.
This article covers what the research and the lived experience of diabetic endurance athletes actually show about riding with diabetes. Not the motivational version. The practical version — the one that keeps you safe on the bike and performing at a level your condition does not need to limit.
Two Conditions, Two Different Responses to Exercise
Type 1 and type 2 diabetes share a name and a blood glucose problem, but the underlying mechanism is different, and that difference matters enormously on the bike.
Type 1 is an autoimmune condition. Your immune system destroyed the beta cells in your pancreas that produce insulin. You inject insulin (or use a pump) to replace what your body cannot make. The critical problem during exercise is that injected insulin does not self-regulate. A working pancreas reduces insulin output within minutes of exercise starting. Your insulin pump or long-acting injection does not know you have just started a two-hour ride. The insulin keeps working. Glucose keeps dropping. Hypoglycaemia becomes the primary risk during and for hours after the session.
Type 2 is primarily an insulin resistance problem. Your pancreas still produces insulin — often more than normal — but your cells respond poorly to it. Exercise improves that response. Endurance work like cycling is one of the most effective interventions for type 2 diabetes because it directly addresses insulin sensitivity in skeletal muscle, which is your largest glucose disposal tissue. The risk profile during exercise depends heavily on medication. Metformin alone carries minimal hypoglycaemia risk. Sulfonylureas increase it. Insulin therapy for type 2 brings many of the same exercise considerations as type 1.
The practical implication: a type 1 cyclist's primary concern on the bike is preventing blood sugar from dropping too low. A type 2 cyclist's primary concern is usually managing blood sugar that is chronically too high, with exercise being a powerful tool to bring it down. Different starting points. Different risk profiles. Different fuelling strategies.
Both conditions benefit enormously from cycling. But the management is not interchangeable, and the advice that works for one may be wrong for the other.
The Insulin Sensitivity Window
Every time you ride, you open a window of improved insulin sensitivity that lasts 24 to 48 hours. This is one of the most powerful physiological effects of endurance exercise for anyone with diabetes, and it is worth understanding why.
During exercise, your working muscles take up glucose through a mechanism that is partly independent of insulin. GLUT4 transporters — the proteins that move glucose from your blood into muscle cells — are activated by muscle contraction itself, not just by insulin signalling. This means that even in insulin-resistant type 2 cyclists, exercising muscles are pulling glucose out of the bloodstream more effectively than they do at rest.
After the ride, the effect continues. Your muscles need to replenish glycogen stores, and the insulin sensitivity of those muscles remains elevated for 24 to 48 hours post-exercise. Research from Richter and Hargreaves — published in Physiological Reviews — shows that a single 60-minute moderate-intensity cycling session can reduce blood glucose by 2 to 3 mmol/L and improve glucose disposal rates for the remainder of the day.
For type 2 cyclists, this is the mechanism that makes consistent riding so effective. Not one epic ride per week. Consistent moderate volume — four to five days of riding — keeps the insulin sensitivity window effectively open all the time. The HbA1c improvements seen in exercise trials for type 2 diabetes are driven by this cumulative window effect, not by any single session.
For type 1 cyclists, the same window creates a risk. Improved insulin sensitivity after a ride means that your normal insulin dose may be too much for the next 24 to 48 hours. Late-onset hypoglycaemia — a blood sugar crash six to twelve hours after exercise — is one of the most dangerous patterns for type 1 athletes. It often strikes overnight. Reducing basal insulin rates by 10 to 20 per cent on training days, and monitoring glucose closely through the night after hard sessions, is standard practice among experienced type 1 endurance athletes.
CGMs on the Handlebars: Real-Time Data That Changes Everything
The continuous glucose monitor has done for diabetic athletes what the power meter did for cycling training. Before CGMs, managing blood sugar on the bike meant stopping to prick your finger, waiting for a result, and making decisions based on a single point in time. Now you have a real-time trend line on your handlebars.
Dexcom G7, Abbott Libre 3, and Medtronic Guardian all provide continuous glucose readings that can be displayed on a cycling computer, phone mount, or smartwatch. The data updates every one to five minutes. And the critical insight that experienced diabetic cyclists learn quickly is that the trend matters more than the number.
A glucose reading of 7 mmol/L means something completely different depending on whether it is stable, rising, or falling. A stable 7 is comfortable. A 7 that is falling at 0.1 mmol/L per minute means you will be at 4 inside 30 minutes if you do nothing. A 7 that is rising after a hard interval is the adrenaline response doing its thing — no intervention needed.
The rate of change arrow on your CGM is your most important piece of on-bike data. Flat arrow: carry on. Single downward arrow (falling 0.06 to 0.1 per minute): eat 15 to 20 grams of fast-acting carbohydrate now. Double downward arrow (falling more than 0.1 per minute): stop, eat, wait, confirm the trend has reversed before continuing.
Some practical points on CGM placement for cyclists. The back of the upper arm — the standard placement for Libre sensors — works well under a jersey sleeve. Ensure the sensor is not directly under a jersey seam or bib strap. Apply a skin adhesive patch or overlay tape for sweaty conditions. Carry your phone or receiver where you can glance at it without taking your hands off the bars.
For type 1 cyclists using insulin pumps, the combination of CGM and pump — particularly hybrid closed-loop systems like the Medtronic 780G or the CamAPS FX algorithm — adds a layer of automated insulin adjustment. These systems reduce basal delivery when glucose is trending low. They do not eliminate the need for manual intervention during exercise, but they reduce the cognitive load substantially.
Pre-Ride Fuelling: The Buffer Zone
The 60 to 90 minutes before a ride is where type 1 cyclists either set themselves up for a safe session or create a problem they will spend the first hour trying to fix.
The target is to start the ride with blood glucose between 7 and 10 mmol/L. Below 7, you have insufficient buffer against exercise-induced drops. Above 10, you are starting in a hyperglycaemic state that impairs performance and creates its own problems — dehydration, poor gastric emptying, and reduced power output.
For a type 1 cyclist eating a meal before riding, the standard approach is to reduce the bolus insulin for that meal by 25 to 50 per cent. The exact reduction depends on your individual insulin sensitivity, the duration and intensity of the planned ride, and whether you are using rapid-acting or ultra-rapid-acting insulin. Dr Michael Riddell's research group at York University — which has published extensively on exercise and type 1 diabetes — recommends the 50 per cent bolus reduction as a starting point for moderate-intensity sessions lasting 30 to 60 minutes.
The meal itself should be moderate glycaemic index. Not a pure sugar spike that will crash before you clip in. Not a slow-release meal that has not been absorbed when you start riding. Something like porridge with banana, or toast with peanut butter and a piece of fruit, eaten 60 to 90 minutes before the ride. This gives the meal time to digest, the reduced bolus time to act, and your blood glucose time to settle into that 7 to 10 range.
For type 2 cyclists on metformin, the pre-ride window is less fraught. Metformin does not cause hypoglycaemia on its own, so a normal pre-ride meal with normal timing works. If you are on a sulfonylurea or insulin, apply the same buffer-zone logic as type 1: check glucose before starting, ensure you are above 7 mmol/L, carry fast-acting carbohydrate from the first pedal stroke.
Morning fasted rides deserve a specific mention. For type 2 cyclists on metformin alone, short fasted sessions (under 90 minutes, zone 2) are generally manageable, though you should still check glucose before starting. For type 1 cyclists, fasted riding without insulin adjustment is high risk. The combination of overnight fasting and exercise-induced glucose uptake can produce rapid drops that catch you before you feel them. If you want to ride fasted as a type 1 athlete, this is a protocol to develop with your endocrinologist, not something to experiment with alone.
Why Hard Intervals Spike Your Glucose
This is the one that confuses almost every diabetic cyclist the first time it happens. You finish a hard interval set, check your glucose, and it is higher than when you started. You expected exercise to bring it down. Instead it went up.
The mechanism is the counterregulatory hormone response. High-intensity exercise — anything above about 80 per cent of VO2max — triggers a significant release of adrenaline and cortisol. These hormones stimulate your liver to dump stored glycogen into the bloodstream as glucose. In a person with normal insulin function, the pancreas responds by increasing insulin output, and the spike is buffered. In a person with type 1 diabetes, or advanced type 2 with impaired insulin secretion, the liver glucose hits the bloodstream with no matching insulin response. Blood sugar climbs.
The spike is typically 2 to 5 mmol/L above baseline and resolves within 60 to 90 minutes after the hard effort ends, as the adrenaline clears and either injected insulin or residual endogenous insulin brings glucose back down.
The mistake is to correct the spike aggressively with insulin immediately after hard intervals. The glucose is already on its way down once the stress hormones clear. Adding a correction bolus on top of the post-exercise insulin sensitivity increase can produce a sharp hypoglycaemic crash two to three hours later. Experienced type 1 athletes learn to wait. Check the trend on your CGM. If glucose is high but the trend arrow is flat or starting to fall, let it resolve on its own. Correct only if it remains elevated beyond 90 minutes post-exercise.
This has a practical training implication. If your sessions consistently include VO2max intervals and tempo work, expect different glucose patterns from different parts of the session. The warm-up and cool-down will lower glucose. The hard blocks in the middle may raise it. The net effect over a full session depends on the balance of intensity and duration.
Zone 2 and the Case for Consistent Volume
For glucose management specifically — not just fitness — zone 2 riding is the most effective training intensity for diabetic cyclists. The reasons are physiological.
At zone 2 intensity (roughly 60 to 75 per cent of FTP, or a pace where you can hold a conversation with some effort), your muscles are primarily burning fat with a moderate contribution from glucose. The glucose uptake is steady and predictable. The stress hormone response is minimal, so you avoid the liver glucose dump that hard efforts trigger. Blood sugar trends downward in a controlled, manageable way.
This is where the CGM data becomes invaluable for training prescription. Over weeks of riding with a CGM, you build a personal library of how your glucose responds to different intensities, durations, and fuelling strategies. You learn that a two-hour zone 2 ride with 30 grams of carbohydrate per hour holds your glucose between 5 and 7. You learn that adding a 10-minute tempo block in the middle causes a transient 1 mmol/L rise that settles within 20 minutes. You learn your own patterns.
For type 2 cyclists, consistent zone 2 volume is the primary exercise prescription for improved glucose control. The research is clear: four to five sessions per week of moderate-intensity aerobic exercise, totalling 150 to 300 minutes, produces clinically significant improvements in HbA1c, fasting glucose, and insulin sensitivity. The improvement is dose-dependent up to about 300 minutes per week — more riding, better numbers, until the returns flatten.
For type 1 cyclists, zone 2 volume is the most manageable intensity from a glucose-management perspective because the glucose trend is predictable and the fuelling requirement is consistent. Hard interval days require more active management. Zone 2 days allow you to ride with a simpler protocol.
The broader training point stands: zone 2 should form 75 to 80 per cent of your total training volume regardless of diabetes. The metabolic benefits simply compound the performance benefits for cyclists managing blood sugar.
Strength Training: Your Glucose Disposal Insurance
Skeletal muscle is your body's primary glucose disposal site. The more muscle mass you have, and the more insulin-sensitive that muscle is, the better your glucose regulation. This is true for everyone, but it is especially important for cyclists with diabetes.
Resistance training improves insulin sensitivity through mechanisms that are partly independent of aerobic exercise. The GLUT4 transporter upregulation from resistance work persists for 24 to 48 hours post-session, similar to endurance exercise. But resistance training also increases total muscle mass — which increases the total glucose disposal capacity of your body. For type 2 cyclists, this is a structural improvement that compounds over months and years.
Two to three resistance sessions per week, focusing on movements that build and maintain the muscles cyclists tend to lose: leg press, lunges, step-ups, hip thrusts, and upper-body pulling and pressing work. The protocol does not need to be complicated. Moderate loads, controlled movement, progressive overload over time. The strength training for cyclists guide covers the specifics.
For glucose management, the timing of resistance training matters. Blood sugar response to strength work is more variable than aerobic exercise. Some athletes see a drop during the session. Others see a rise — particularly during high-effort sets that trigger the same stress hormone response as hard intervals. Monitor your CGM during your first several strength sessions to learn your personal pattern, then adjust fuelling and insulin accordingly.
The combination of cycling and resistance work is more effective for glucose control than either alone. A 2020 meta-analysis in Diabetes Care found that combined aerobic and resistance training produced greater HbA1c reductions than either modality in isolation. For masters cyclists managing type 2 diabetes, this is the strongest argument for keeping strength training in the programme year-round.
Race Day With Diabetes
Race day adds adrenaline, nerves, unpredictable pacing, and limited access to your usual management tools. It also adds a level of intensity that most training sessions do not reach. All of this affects glucose regulation.
The protocol starts the night before. Check that your CGM sensor is fresh (not due for replacement mid-race) and securely adhered. Lay out your on-bike nutrition with extra fast-acting glucose — at least double what you would carry for a training ride of the same duration. Prepare a jersey pocket or top-tube bag that is reachable at speed.
Morning of the race: eat your pre-ride meal at the usual 60 to 90 minutes out. For type 1 cyclists, reduce bolus as you would for training, but consider an additional 10 to 15 per cent reduction because race-intensity adrenaline will trigger more hepatic glucose output than a training ride. Check glucose 30 minutes before start and again at the line. Target that 7 to 10 mmol/L window. If you are below 7, eat 15 to 20 grams of carbohydrate and wait for the trend to confirm a rise before starting.
During the race, glucose management becomes simplified by necessity: eat more than you think you need. A conservative fuelling plan that errs on the side of more carbohydrate is safer than an aggressive plan that risks a hypo mid-race. For type 1 cyclists, 45 to 60 grams of carbohydrate per hour from the start is a reasonable baseline — higher than many non-diabetic cyclists use — because you are fuelling against both exercise glucose uptake and circulating insulin.
Brief your riding partners or race support. Tell someone you are riding with that you have diabetes, where your glucose tablets are, and what to do if you signal distress. This is not weakness. Phil Southerland's Team Novo Nordisk riders brief their team car on individual insulin protocols before every stage. Professional management requires communication.
After the race, the heightened insulin sensitivity period is longer and more pronounced than after a normal training ride. Monitor glucose for at least 12 to 24 hours post-race. Reduce basal insulin rates if you use a pump. Eat a carbohydrate-containing recovery meal within 30 to 60 minutes of finishing. Set an alarm to check glucose before bed and again at 3am if you have had a particularly hard effort — nocturnal hypoglycaemia after race day is a real risk for type 1 athletes.
Working With Your Medical Team
The gap between a standard diabetes care appointment and what a diabetic athlete needs is often enormous. Most GPs and many endocrinologists do not have sports-specific diabetes expertise. Their advice tends toward caution — "be careful with exercise" — without the specificity that lets you actually train effectively.
Find an endocrinologist or diabetes specialist nurse who works with athletes, or at minimum one who is willing to learn. The questions you need answered are specific: how much should I reduce my basal rate for a two-hour ride? What bolus adjustment should I make for a pre-ride meal before intervals versus before zone 2? What is my target glucose range during exercise? These are not questions a ten-minute GP appointment can address.
Bring data. CGM downloads showing your glucose traces during rides. Training logs with session type, duration, intensity, and fuelling notes alongside glucose outcomes. The more data you bring, the more specific the advice you get back. An endocrinologist looking at 30 days of CGM traces overlaid with training data can spot patterns you would never identify from finger pricks alone.
Diabetes UK's sport and exercise resources, and the JDRF's athlete programme, are both good starting points for finding sports-aware clinicians. Internationally, the ISPAD (International Society for Pediatric and Adolescent Diabetes) exercise guidelines are applicable to adult athletes and represent the most current consensus on type 1 diabetes and exercise management.
Never adjust medication doses based on something you read online — including this article. Use the information here to inform the conversation with your medical team, not to replace it. The specifics of your insulin regimen, your medication, your individual glucose response, and your training demands are unique to you. A guide can tell you what questions to ask. Only your clinical team can give you the answers that are safe for your body.
Riding Without Limits
Diabetes adds a layer of management that non-diabetic cyclists never think about. Every ride involves an additional calculation. Every meal before a session carries an additional variable. Race day has an additional protocol. The cognitive load is real, and pretending otherwise does nobody any favours.
But the ceiling on what you can achieve as a cyclist with diabetes is not set by the condition. It is set by the same things that limit every other rider — consistency, training quality, recovery, fuelling, and the willingness to keep showing up when the process is hard. Team Novo Nordisk races Grand Tour stages. Diabetic age-group athletes finish Ironman events and ultra-distance rides and national championships. The condition is a constraint to manage, not a reason to settle.
The combination of CGM technology, modern insulin delivery systems, and the accumulated knowledge from athletes who have done this before you means that you have better tools than any previous generation of diabetic cyclists. Use them. Track your data. Learn your patterns. Work with a medical team that understands what you are asking your body to do. And ride.
If you are managing diabetes alongside your cycling and want to train with riders who take their performance seriously — without pretending that health conditions do not exist — the Roadman community at Not Done Yet is where we do that work. The conversation is ongoing, the support is real, and nobody there is settling for less than they are capable of.