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Dawn Phenomenon vs. Somogyi Effect

What is the dawn phenomenon that some people with diabetes experience?1

The dawn phenomenon, also called the dawn effect, is the term used to describe an abnormal early-morning increase in blood sugar (glucose) — usually between 2 a.m. and 8 a.m. — in people with diabetes.


How does it happen?1

Some researchers believe the natural overnight release of the so-called counter-regulatory hormones — including growth hormone, cortisol, glucagon and epinephrine — increases insulin resistance, causing blood sugar to rise. High morning blood sugar may also be caused by insufficient insulin the night before, insufficient anti-diabetic medication dosages or carbohydrate snack consumption at bedtime.

If you have persistently elevated blood sugar in the morning, checking your blood sugar once during the night — around 2 a.m. or 3 a.m. — for several nights in a row will help you and your doctor determine if you have the dawn phenomenon or if there’s another reason for an elevated morning blood sugar reading.


What can you do?1

Your doctor may recommend a number of options to help you prevent or correct high blood sugar levels in the morning:

  • Avoid carbohydrates at bedtime.
  • Adjust your dose of medication or insulin.
  • Switch to a different medication.
  • Change the time when you take your medication or insulin from dinnertime to bedtime.
  • Use an insulin pump to administer extra insulin during early-morning hours.


Now that we have explored the dawn phenomenon, let’s take a look at the Somogyi effect.


What is the Somogyi effect?2

Also known as the Somogyi phenomenon, the Somogyi effect (aka post-hypoglycemic hyperglycemia, chronic Somogyi rebound) describes a rebound high blood glucose level in response to low blood glucose.

Amongst those people with diabetes who manage their blood glucose using insulin injections, this may take the form of high blood sugar in the morning due to an excess amount of insulin during the night.


How does it happen?2

Somogyi – a Hungarian-born professor after whom the phenomenon was named – theorized that prolonged levels of untreated hypoglycemia could lead to stress (due to low blood sugar) and a high blood sugar levels rebound.

This is a defensive response by the body as it released endocrine hormone glucagon, backed up by the stress hormones cortisol and epinephrine.

This means an instant increase in blood glucose, and stress hormones cause insulin resistance for several hours, and this in turn leads to elevated blood sugar.


Does the Somogyi phenomena only occur during the night?2

Sometimes the Somogyi rebound will occur when the person with diabetes is awake.
They may notice initial symptoms of low blood sugar or a rebound.
Waking up during the night is a clear symptom of the Somogyi effect.
The evidence indicates that most people with type 1 diabetes who experience nocturnal Somogyi effect do not usually wake up.


Is Somogyi Effect the same as Dawn Phenomenon?2

No, although they are often confused by healthcare professionals.

The Dawn Effect (or Dawn Phenomenon) is a morning rise in blood sugar which occurs as a response to waning levels of insulin and a surge in growth hormones.


What can you do to avoid Somogyi Effect?2

Somogyi Effect is avoidable in several ways. Firstly, intense blood glucose testing allows the individual experiencing Somogyi effect to detect and then prevent the circumstances leading to it.

Testing blood sugar regularly using a traditional blood glucose meter helps to catch low blood sugar levels before any rebound occurs.

Night testing of blood glucose levels is also important, and adjusting insulin in response may also be appropriate.

Somogyi rebound can be a challenge to avoid. The need to keep blood sugar levels stable whilst still adjusting insulin to take account of a complex lifestyle involving stress and exercise can be really difficult.

Practical ways to avoid Somogyi effect include regular blood glucose monitoring, logging blood glucose values, conservatively increasing insulin, being aware of hypoglycemia and how your insulin influences it, and using the most suitable insulin for your circumstances.


Talk to your doctor if you believe you’re experiencing either Dawn Phenomenon or the Somogyi Effect.


References: 1. Mayo Clinic. 2020. The Dawn Phenomenon: What Can You Do?. [online] Available at: <,a.m.%20%E2%80%94%20in%20people%20with%20diabetes.> [Accessed 9 August 2020]. 2. 2019. The Somogyi Phenomenon (Also Known As Post-Hypoglycemic Hyperglycemia, Chronic Somogyi Rebound) Describes A Rebound High Blood Glucose Level In Response To Low Blood Glucose. [online] Available at: <> [Accessed 9 August 2020].

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