Why Your Blood Sugar Is Running the Show (Even If You're Not Diabetic)

I'd say at least half the women who sit across from me have never had a conversation about their blood sugar. Not once. Unless you've been told you're diabetic or pre-diabetic, it rarely comes up. And yet so much of what brings people into my clinic, the 3pm energy crash, the 2am waking, the mood swings that seem to come from nowhere, the weight that won't shift no matter what you try, traces straight back to how well your blood sugar is being regulated.

This isn't a diabetes conversation. It's a foundational one. Blood sugar regulation is one of the most tightly controlled systems in the entire body, and when it's running well, you genuinely don't notice it. When it's not, it touches almost everything else, your hormones, your sleep, your mood, your energy, your skin.

So let's start at the beginning.

The tightrope your body is always walking

Healthy blood glucose sits in a narrow band, roughly 4.7 to 5.6 mmol/L, and your body works constantly, automatically, to keep it there. Too low and your cells are starved of fuel. Too high and that excess glucose starts to damage tissue. Neither extreme is somewhere your body wants to live, so it has built an elegant, fast-acting system to keep you balanced.

Here's what makes this especially relevant for mood and energy: your brain cells take up glucose independently of insulin, through receptors called GLUT1 and GLUT3. That means your brain feels the effects of a blood sugar swing almost immediately, before the rest of your body has caught up. It's a big part of why a dip in blood sugar can tip you into anxiety, brain fog or a sudden low mood within minutes, not hours.

Three fuels, one priority order

Your body has three sources of fuel, and it reaches for them in a specific order.

Glucose, from carbohydrate, is the preferred and fastest source. Your brain alone uses around 120g of it a day.

Fatty acids and ketones are the backup fuel, used during fasting or longer exercise. The catch is that when insulin is high, those stored fats are essentially locked away and inaccessible. Your body cannot burn fat for fuel and run high insulin at the same time. This is one of the most practical things to understand if weight loss has felt impossible.

Amino acids, from protein, are the fuel of last resort. Your body only turns to breaking down protein for energy when it's truly run out of other options, and it's metabolically expensive and inefficient to do so.

Where your circulating glucose actually comes from

Three processes keep glucose available in your bloodstream.

After a meal, glucose is absorbed across the gut wall. How quickly depends heavily on how much fibre and fat is in that meal, which is why a piece of toast alone hits you very differently to that same toast with eggs and avocado.

Between meals, your liver can manufacture new glucose, a process called gluconeogenesis. This is switched on by cortisol, so it ramps up under stress, illness, or even intense exercise. It's a major reason chronically stressed people often run higher blood sugar even without eating more.

And your liver holds a reserve of stored glucose, called glycogen, which it can break down on demand. That reserve is roughly a 12 hour supply. Your muscles store glycogen too, around four times as much as the liver, but that stash is locked for local use only. It fuels your muscles, not your brain.

The hormones running the show

A handful of hormones, made in your pancreas, are constantly negotiating to keep you in that narrow target range.

Insulin is your storage hormone. When blood glucose rises after eating, your pancreas releases insulin, which acts like a key, unlocking your cells so glucose can move in and be used for energy or stored as glycogen. In insulin resistance, that key essentially stops working properly. The glucose transporters sit uselessly inside the cell instead of coming up to the surface to do their job, so glucose builds up in the blood instead of getting where it's needed.

Glucagon is insulin's counterpart, released when blood sugar drops, prompting the liver to release its stored glucose back into circulation.

Amylin is released alongside insulin and plays a quieter but important role: it slows gastric emptying and signals satiety, which is part of why a meal with adequate protein leaves you genuinely full rather than hunting for something sweet twenty minutes later.

Somatostatin is the safety brake. It keeps both insulin and glucagon from overshooting, preventing the kind of dramatic swing that leaves you crashing. Interestingly, this hormone goes up just from smelling food before you eat it, which is a lovely bit of physiology backing up something we already say constantly in clinic: slow down, sit down, and actually notice your meal before you eat it. Your nervous system needs to be in a parasympathetic, rest and digest state for this whole system to work as it should.

The appetite hormones nobody told you about

This is where it gets genuinely interesting, because this is the part of the system behind the new generation of weight loss medications, and you can support it yourself, for free, with how you structure your meals.

A group of hormones called incretins are released from your gut in response to food, and they act before your blood glucose even has the chance to rise. The most well known is GLP-1, made by cells in your small intestine. Within minutes of food reaching your gut, GLP-1 stimulates a first wave of insulin release, slows down how quickly your stomach empties, and sends signals to your brain that you're satisfied. This is the exact pathway that drugs like Ozempic work on.

The encouraging part is that you have the ability to stimulate your own GLP-1 naturally. Fibre, broken down by your gut bacteria into short chain fatty acids, is one of the strongest triggers. Protein and amino acids are another. So is bitter food.

In practice, this means the order you eat your food in matters. Starting a meal with protein, or even a small bitter starter, primes this entire satiety cascade before the carbohydrate-heavy part of your meal arrives. It's a genuinely simple shift with an outsized effect.

Why this matters more than you think

When this whole system is working well, you don't think about it. You wake up with a normal appetite, your energy stays steady through the day, and meals neither spike you nor crash you. When it's not working well, the knock-on effects are wide-reaching: fatigue, disrupted sleep, mood swings, anxiety, hair thinning, fertility and hormonal imbalance, and that frustrating sense that your metabolism simply won't cooperate with weight loss, however hard you try.

In my next post, I'll walk you through what dysregulated blood sugar actually feels like day to day, the difference between running too low and too high, and why so many women are dealing with this without ever knowing it has a name.

If you suspect your blood sugar might be part of your picture, book a consultation here and we can look at your full health picture together.