What Causes Blood Sugar Spikes (Even Without Diabetes)?

Blood sugar can rise after eating — that is a normal part of how the body uses food for energy. A “spike” usually refers to a bigger or faster rise than expected, or readings that are frequently above the target set by your healthcare team.

Food and drink

Meals high in refined carbohydrates or sugary drinks can raise glucose quickly. Portion size and the balance of protein, fibre and fat in a meal can also affect how quickly glucose changes.

That does not mean you need to label foods as “good” or “bad.” A registered dietitian or diabetes team can help you make changes that suit your lifestyle.

Stress and poor sleep

Stress hormones can affect blood glucose. Poor sleep can also make blood sugar harder to manage for some people.

If you notice a pattern after busy weeks or disrupted nights, make a note of it rather than blaming yourself for a single reading.

Illness, inactivity and medication

Infections and other illnesses can raise blood sugar. Less activity than usual may also affect it, as can some medicines such as steroids.

If you have diabetes, follow your sick-day rules and contact your care team if you are unsure what to do.

What to do if spikes are frequent

Regular high readings are worth discussing with a GP or diabetes team. Do not adjust prescribed medicine without advice.

Logging the time, food context, activity and readings can make patterns easier to see. Use Pulse to track your glucose trend.