The Somogyi Effect: A Night Low That Hides Behind a Morning High

Chapter 18 · Vihang Rahul Vasa

Sometimes a high fasting plasma glucose (blood sugar) reading in the morning is not what it looks like. One possible explanation, long taught, and now thought to be less common than once believed, goes like this. If your night-time medicine, insulin or strong tablets, has pulled your plasma glucose (blood sugar) too low while you sleep, your body panics and rescues you by releasing stored glucose from the liver. It rescues a little too well, and you wake up with a high number. This is the Somogyi effect, and it is caused by the medicine acting too strongly at night. The dawn phenomenon, explained in the next chapter, is different: that morning rise comes from your body’s own early-morning hormones and happens even in people taking no medicine at all. Why does the difference matter? Because the wrong guess leads to the wrong action: seeing a high morning number, many people increase their night dose, which makes the hidden night lows even worse. So never adjust any dose yourself. Simply tell your doctor about your high morning readings: they may ask you to check your plasma glucose (blood sugar) around 2–3 AM for a few nights, or suggest a CGM, and the pattern will reveal the true story. Remember the clear difference: the Somogyi effect happens only with stronger night-time medicines, while the dawn phenomenon can affect you even without any night medicines at all. Let your doctor, not guesswork, decide.

Illustration: Chapter 18 illustrated summary. The possible Somogyi rebound pattern shows medicine acting too strongly at night, a night-time low, the liver releasing stored glucose, and a higher morning reading.

Chapter 18 The possible Somogyi rebound pattern shows medicine acting too strongly at night, a night-time low, the liver releasing stored glucose, and a higher morning reading. The figure says this is less common than once believed. CGM helps investigate overnight patterns; increasing the night dose can worsen a low, and dose decisions remain doctor-led.

Chapter at a glance: an AI-generated illustration to be read with the chapter, not instead of it. The people shown are not real.