Surreal image of a blood drop becoming a sugar cube, symbolizing blood sugar balance.

Unexplained Low Blood Sugar? A Guide to Hypoglycemia in Non-Diabetics

Jordan Keane in Health & Wellness December 2025 • 4 min read.

"Decoding the Mystery: Symptoms, Diagnosis, and What to Do When Your Blood Sugar Drops Too Low"

It's a common scenario: someone feels unwell and suspects low blood sugar (hypoglycemia). But true, organic hypoglycemia – that is, hypoglycemia with a clear medical cause – is actually quite rare in people without diabetes. More often than not, these episodes turn out to be something else.

Genuine hypoglycemia needs to be considered, especially if there are predisposing factors. These include problems with the adrenal glands, general wasting away (cachexia), or in elderly patients with multiple medical conditions. Also, if someone has symptoms that suggest the brain isn't getting enough glucose (neuroglucopenia), it could point towards a rare condition called an insulinoma.

The key to diagnosing such cases is proving that the body is producing too much insulin when blood sugar levels are low. This usually involves a carefully monitored fasting test in a hospital setting.

What Exactly is Hypoglycemia?

Surreal image of a blood drop becoming a sugar cube, symbolizing blood sugar balance.

In the context of diabetes, hypoglycemia is very well defined. However, outside of diabetes, the definition relies on what's called "Whipple's triad." This means three things need to be present:

You have symptoms that could be caused by low blood sugar.
Your blood sugar level is actually low when measured.
Your symptoms get better quickly after you take glucose (sugar).

Symptoms that could be caused by low blood sugar;
Your blood sugar level is actually low when measured;
Your symptoms get better quickly after you take glucose (sugar).

It's important to note that blood sugar levels are measured from venous blood, meaning blood drawn from a vein. Readings from finger-prick tests (capillary blood) aren't reliable enough to make a diagnosis on their own. Different organizations have slightly different cut-off points for what constitutes low blood sugar. Some use a threshold of 0.55 g/L (3 mmol/L), while others use 0.5 g/L (2.75 mmol/L) to improve the accuracy of diagnosis. For elderly patients, levels below 0.65 g/L (3.6 mmol/L) might warrant further investigation. In short, true hypoglycemia (outside of diabetes) means having those typical symptoms, a venous blood sugar level below 0.5 g/L (2.75 mmol/L), and feeling better after getting some sugar.

The Bottom Line

If you suspect you're experiencing hypoglycemia, especially without having diabetes, it's essential to consult a healthcare professional. A detailed medical history and physical exam can help identify any obvious causes or signs of organic hypoglycemia. If organic hypoglycemia is suspected, a carefully monitored fasting test in a specialized hospital setting is often necessary to determine the underlying cause and ensure proper management.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1016/s1636-5410(17)86024-4, Alternate LINK

Title: Sospecha De Hipoglucemia En El Adulto No Diabético

Subject: General Medicine

Journal: EMC - Tratado de Medicina

Publisher: Elsevier BV

Authors: C. Amouyal

Published: 2017-09-01

Everything You Need To Know

What exactly defines hypoglycemia in someone who doesn't have diabetes, and why is it important to know?

Hypoglycemia, in the context of non-diabetics, is characterized by the presence of Whipple's triad. This triad consists of three specific criteria: experiencing symptoms suggestive of low blood sugar, having a measured venous blood sugar level below a certain threshold (typically 0.5 g/L or 2.75 mmol/L), and a quick resolution of symptoms upon glucose intake. It's significant because it helps differentiate true low blood sugar from other conditions that might mimic its symptoms.

What is neuroglucopenia, and why is it important to identify?

Neuroglucopenia arises when the brain doesn't get enough glucose. Identifying it is significant because it might point towards rare conditions like insulinoma, where the body produces too much insulin. Diagnosing neuroglucopenia often requires carefully monitored fasting tests to assess insulin levels and identify the underlying cause.

What do healthcare professionals look for when trying to determine the underlying cause of hypoglycemia?

When hypoglycemia is suspected, healthcare professionals look for underlying causes. This involves reviewing a patient's medical history and performing a physical exam to identify factors like adrenal gland problems or cachexia. The detection of these predisposing factors is crucial as they can contribute to organic hypoglycemia. This step is essential for targeted diagnosis and management.

What is a fasting test, and why is it conducted in a hospital setting?

A fasting test in a hospital setting is conducted when organic hypoglycemia is suspected. This test involves monitoring blood sugar levels over a period to determine if the body is producing too much insulin when blood sugar levels are low. The purpose of the test is to establish a definitive diagnosis and guide appropriate treatment strategies for the underlying cause of hypoglycemia. The test is only performed if organic hypoglycaemia is suspected.

Why is venous blood used to measure blood sugar levels for diagnosing hypoglycemia, and what cut-off points are used?

Venous blood is used to measure blood sugar levels for diagnosing hypoglycemia because it offers a more reliable and accurate assessment compared to finger-prick tests that use capillary blood. The cut-off points defining low blood sugar (0.55 g/L or 3 mmol/L, or even 0.5 g/L or 2.75 mmol/L in some cases) are based on venous blood measurements. This is important because using venous blood ensures more precise diagnostic criteria are met.