“Hypo” can mean a few different things, depending on context, but two uses are by far the most common:

1. In everyday medical/diabetes talk

In health and diabetes discussions, “a hypo ” is short for hypoglycaemia – an episode where your blood sugar level drops too low and can make you feel unwell, shaky, confused, sweaty, hungry, or even cause collapse if severe.

People with type 1 or type 2 diabetes who use insulin or certain tablets often say things like “I had a hypo last night” to mean they had low blood sugar and needed fast-acting sugar (like juice or glucose tablets) to bring it back up.

Typical “hypo” (low blood sugar) signs

  • Shaking or trembling, feeling jittery.
  • Sweating, palpitations, feeling suddenly anxious.
  • Hunger, dizziness, blurred vision, trouble concentrating.
  • In more severe cases, confusion, behavior changes, or loss of consciousness.

If someone is talking about diabetes, they almost always mean this when they say “a hypo.”

If you or someone around you has diabetes and might be having repeated or severe hypos, it’s important to speak to a doctor or diabetes nurse promptly for personalized advice.

2. As a medical/scientific prefix “hypo-”

“Hypo-” is also a prefix in medical and scientific words that means low, under, or below normal , like in:

  • Hypoglycemia – low blood sugar.
  • Hypotension – low blood pressure.
  • Hypothermia – abnormally low body temperature.

In this sense it’s the opposite of “hyper-”, which means “high” or “above normal” (for example, hyperglycemia = high blood sugar).

3. In chemistry / photography (“hypo” the chemical)

In older chemistry and photography contexts, “hypo” is a nickname for sodium thiosulfate , historically called sodium “hyposulphite.”

  • Chemical name: sodium thiosulfate, often written as Na₂S₂O₃.
  • Use: classic photographic fixer ; it removes unreacted silver halide from film or photographic paper so the image is stabilized.

If someone is talking about darkroom photography or old-school film processing, that’s probably what they mean by “hypo.”

Which meaning fits “what is hypo”?

  • Talking about diabetes, blood sugar, or health → they almost certainly mean a low blood sugar episode (a hypo).
  • Talking more generally in medical/science terms → they might mean the prefix “hypo-” = low or under.
  • Talking about chemistry or film photography → they probably mean sodium thiosulfate fixer.

If you tell me the context (health, school, photography, etc.), I can narrow it down to the exact sense you need. Information gathered from public forums or data available on the internet and portrayed here.