# Sleep and type 2 diabetes: how short sleep affects blood sugar

Source: https://sleepfacts.uk/benefits/type-2-diabetes/
Author: Tess Marlow · Updated 2026-11-04

**Short answer:** In studies of over 100,000 people, short sleep raised the risk of developing type 2 diabetes by about 28%, and trouble staying asleep by 84%. Lab trials show why: a few nights of short or shallow sleep make the body less sensitive to insulin, so blood sugar control worsens even in healthy young people.

**Evidence grade:** Moderate evidence. Trials point the same way but are small or few, or large long-term studies agree but cannot prove cause and effect.

## What do the long-term studies show?

A 2010 review pooled 10 studies with 107,756 people followed for 4 to 32 years, during which 3,586 developed type 2 diabetes. Compared with people who slept well:

| Sleep at the start | Higher risk of type 2 diabetes |
| --- | --- |
| Short sleep (5 to 6 hours or less) | 28% |
| Long sleep (8 to 9 hours or more) | 48% |
| Difficulty falling asleep | 57% |
| Difficulty staying asleep | 84% |

These are observational findings, so they can't prove poor sleep causes diabetes. People who sleep badly are more likely to be overweight, stressed or depressed, and to work shifts, all of which affect diabetes risk. The researchers adjusted for many of these factors.

## What do lab trials show?

They show short-term cause and effect in healthy people:

- **Short sleep.** When 11 healthy young men were limited to 4 hours in bed for six nights, their glucose tolerance was lower than when they were fully rested. Evening cortisol and "fight or flight" nervous activity rose too, both of which push blood sugar up.
- **Shallow sleep.** In another study, researchers used sounds to keep young adults out of deep sleep all night without waking them or shortening their sleep. After three nights, their insulin sensitivity fell markedly and their glucose tolerance worsened, and the more deep sleep they lost, the bigger the fall. That suggests deep sleep itself, not just total hours, matters for blood sugar, and may help explain why diabetes risk rises with age, when deep sleep declines.

Short sleep also raises appetite and calorie intake (see [weight and appetite](/benefits/weight-and-appetite/)), which adds to diabetes risk over time.

## Where does sleep apnoea come in?

Obstructive [sleep apnoea](/sleep-problems/sleep-apnoea/) is common in people with type 2 diabetes and shares risk factors with it, especially excess weight. Repeated drops in oxygen and broken sleep worsen insulin resistance. NICE's guideline on sleep apnoea covers assessment for people with symptoms.

## What can you do?

- Aim for 7 to 9 hours of reasonably unbroken sleep.
- Keep a regular schedule. Shift work is linked with higher diabetes risk; see [shift work](/sleep-problems/shift-work/) for ways to limit the damage.
- If you have diabetes or prediabetes and snore loudly, wake unrefreshed or feel sleepy in the day, ask your GP or diabetes team about sleep apnoea.

## Frequently asked questions

### Can poor sleep raise blood sugar?

Yes, at least in the short term. Lab trials in healthy volunteers show that restricted or disrupted sleep reduces glucose tolerance and insulin sensitivity within days. Whether that adds up to diabetes over years is supported by long-term studies but not proven.

### I have diabetes. Does sleep matter?

It may make blood sugar harder to manage, and people with type 2 diabetes have high rates of sleep apnoea. Diabetes UK and the NHS both list sleep as part of looking after yourself. If you snore loudly or wake unrefreshed, ask about sleep apnoea at your diabetes review.

### Does sleeping too much cause diabetes?

Long sleep is linked with diabetes in studies too, but as with heart disease, this probably reflects poor health causing long sleep rather than the reverse.

## References

1. [Cappuccio FP et al. Quantity and quality of sleep and incidence of type 2 diabetes: a systematic review and meta-analysis. Diabetes Care, 2010.](https://pubmed.ncbi.nlm.nih.gov/19910503/)
2. [Spiegel K, Leproult R, Van Cauter E. Impact of sleep debt on metabolic and endocrine function. The Lancet, 1999.](https://pubmed.ncbi.nlm.nih.gov/10543671/)
3. [Tasali E et al. Slow-wave sleep and the risk of type 2 diabetes in humans. PNAS, 2008.](https://pubmed.ncbi.nlm.nih.gov/18172212/)
4. [NICE. Obstructive sleep apnoea/hypopnoea syndrome and obesity hypoventilation syndrome in over 16s (NG202), 2021.](https://www.nice.org.uk/guidance/ng202)