Is it anxiety, or is it low blood sugar?

It is four in the afternoon. Coffee at nine, nothing since, and now your hands are not quite steady, your heart is doing something you can feel, and behind it sits a flat hum of dread you cannot pin to anything. Is that anxiety, or have you just not eaten?

The honest answer is more interesting than the two you normally get offered, which are that blood sugar explains everything and that it explains nothing.

The short version

• Low blood sugar and generalised anxiety disorder (GAD) share four symptoms on the NHS lists, so the two are easy to mix up.
• Genuine low blood sugar is rare without diabetes. If you do not have diabetes and you get shaking, sweating, a fast heartbeat or confusion, that is a GP appointment, not a snack.
• Hunger tracks anger and irritability fairly reliably, and goes with enjoying things less. Whether it produces the wound-up feeling is much less clear.
• Eating at regular times is on the NHS list of things to try. It is not a treatment for an anxiety disorder, and the research cannot say which causes which.

The symptoms genuinely overlap

The NHS list of low blood sugar symptoms reads like a description of a bad afternoon: feeling hungry, feeling dizzy, feeling anxious or irritable, sweating, shaking, tingling lips, heart palpitations, tiredness or weakness, blurred vision, confusion.

The NHS list for GAD is built differently. The main symptom is worry you cannot control, and the rest runs through sleep, restlessness, tension, stomach problems and low mood. But four items sit on both lists: palpitations, dizziness, irritability and tiredness.

You cannot reliably tell the two apart from the inside, because the symptom lists do not tell them apart either.

Genuine low blood sugar is rarer than people think

Here is where the popular version goes wrong. The NHS is direct: low blood sugar mostly affects people with diabetes who take insulin or certain other diabetes medicines, and it is rare in people without diabetes. Where it does happen without diabetes, the causes the NHS names are specific ones. Malnutrition. Addison's disease. A growth in the pancreas.

For most people reading this, "my blood sugar crashed" describes how something felt rather than what was measured. That cuts both ways. A wobbly four o'clock is unlikely to be true hypoglycaemia, which is what a hypo actually is. But if you do not have diabetes and you get shaking, sweating, a fast heartbeat and confusion, NHS advice is to see a GP about it rather than eat more biscuits.

What hunger does do

One useful piece of everyday evidence comes from a study that pinged people five times a day for three weeks, gathering 9,142 reports of how hungry, angry and irritable they felt, and how pleasant things seemed. Sixty-four saw it through to the end. Hungrier moments came with more anger, more irritability and less pleasure, and that held after accounting for age, sex, body mass index, eating habits and how quick-tempered each person was in general.

The interesting part is what did not turn up. The study also measured arousal, the sense of being wound up rather than sleepy, and the researchers had expected hunger to raise it. That association did not reach significance.

The authors are careful with that rather than pleased about it. On their mood grid the hungriest moments still sat in the activated half, just a much less pleasant part of it, and they suggest what goes with hunger may be the combination of high arousal and low pleasure rather than arousal on its own.

Hold all of it lightly: 64 people, mostly young, mostly female, mostly Austrian, everything self-reported, none of them selected for having an anxiety problem, and an association is not a cause. What hunger tracked reliably was anger, irritability and enjoying things less. It is not a clean explanation for feeling frightened.

The question is not only whether missing lunch makes you anxious. It is also whether being anxious is what made you miss lunch.

What the breakfast research can and cannot tell you

You will have seen the headlines about skipping breakfast and mental health. A 2025 review screened 1,671 studies, found 12 that looked at skipping breakfast alongside anxiety and depression, and reported that most found an association. One found none.

Nine of the 12 were cross-sectional, meaning they photograph a group once and look for patterns, which cannot establish cause. And the whole review was about adolescents, not adults.

Its authors are clear about the limitation that matters most: they could not examine whether skipping breakfast leads to poor mental health, or whether existing mental health problems lead to irregular eating. Anyone who has been properly anxious knows appetite is one of the first things to go, so that arrow has a plausible second direction.

What I would do with all this

Eat at roughly regular times. The NHS puts it on its own list of things to try for anxiety: a healthy diet with regular meals, to keep your energy levels stable. It is cheap, and for most people it is an easy thing to test.

This next part is my view rather than the guidance: hold it loosely. The value is not that it treats anything. It is that it removes a variable. If you eat properly for a fortnight and the four o'clock dread is unchanged, you have learned something worth knowing, which is that it was not the sandwich. That leaves you with one clear question instead of a vague sense that something is wrong, and single clear questions are the shape our 20 minute sessions are designed around.

When it is worth seeing someone

Three different situations, and it matters which one you are in.

If the symptoms are the problem, and you do not have diabetes but you get shaking, sweating, a fast heartbeat and confusion, see a GP and describe it in those words.

If the not-eating is the problem, that is a different conversation. Eating very little, strict rules around food, avoiding anything social where food is involved: the NHS lists these among the signs of an eating disorder, and separately names anxiety among the things that make one more likely. Malnutrition, remember, is one of the few things that does cause low blood sugar without diabetes. NHS advice is to see a GP as soon as you can, and you can talk in confidence to the eating disorders charity Beat on 0808 801 0677.

If the anxiety is the problem, the NHS line is that it is more likely to be GAD if you feel anxious most of the time and it affects your everyday life. See a GP, or refer yourself to NHS talking therapies without one if you are 18 or over.

Whichever of those fits, if things feel heavier than that, there is an NHS page on where to get urgent help for mental health, you can call 111 and choose the mental health option, or Samaritans on 116 123. If anyone's life is at risk, or you do not feel you can keep yourself safe, call 999 or go to A&E. brightloaf is not a crisis service.

This article is general information and not a substitute for personal medical advice.