Last Updated on May 12, 2025 by Analgesia team
What Is Deoxyhemoglobin (HHb)?
In medical terms, HHb stands for deoxyhemoglobin, which is unoxygenated haemoglobin. Haemoglobin is a protein in red blood cells that carries oxygen in the blood. When haemoglobin is oxygenated, it’s called oxyhaemoglobin (O2Hb) and is bright red. When deoxygenated, it’s called deoxyhemoglobin (HHb) and is dark red or purple.
Deoxyhemoglobin refers to haemoglobin that has already delivered oxygen to body tissues and is now in its deoxygenated form.
Here’s how it works:
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Oxygen-rich blood leaves the lungs loaded with oxyhaemoglobin (O2Hb)
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As blood circulates, haemoglobin releases oxygen to the tissues
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The haemoglobin becomes deoxyhemoglobin (HHb) and returns to the lungs to pick up oxygen again
This oxygen “handoff” is what keeps your muscles, brain, and organs functioning.
HHb vs O2Hb: What’s the Difference?
| Feature | Oxyhaemoglobin (O2Hb) | Deoxyhemoglobin (HHb) |
|---|---|---|
| Oxygen Status | Bound to oxygen | No oxygen attached |
| Colour | Bright red | Dark red/purple |
| Function | Carries oxygen from lungs to tissues | Returns to lungs after releasing oxygen |
| Clinical Use | Indicates how well oxygen is being delivered | Helps assess tissue oxygen demand and blood return |
Why Is HHb Important in Medicine?
Monitoring HHb and O2Hb levels help assess a person’s oxygenation status — that is, how well oxygen is being delivered and used by the body.
Doctors often look at:
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Oxygen saturation (sO₂) — the percentage of haemoglobin carrying oxygen (O2Hb vs HHb)
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Tissue oxygenation — especially during surgeries or in critical care settings
Too much HHb may signal poor oxygen delivery, while balanced levels indicate healthy oxygen exchange.
Related Haemoglobin Types You Should Know
Not all haemoglobin behaves the same. Here are other variants you might encounter:
1. Carboxyhemoglobin (COHb)
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Haemoglobin bound to carbon monoxide (CO)
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Can’t carry oxygen — dangerous in CO poisoning
2. Methemoglobin (MetHb)
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Haemoglobin with oxidized iron (Fe³⁺)
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Can’t bind oxygen effectively — may occur with certain drugs or chemicals
3. Sulfhemoglobin
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Haemoglobin combined with sulfur
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Rare and also non-functional in oxygen transport
4. Fetal Haemoglobin (HbF)
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Fetal haemoglobin is the main haemoglobin in fetuses
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Has a higher affinity for oxygen than adult haemoglobin — helps babies get oxygen from their mother’s blood
FAQ: Understanding Deoxyhemoglobin
What does HHb mean in medical terms?
HHb stands for deoxyhemoglobin, the form of haemoglobin that does not carry oxygen.
What causes high HHb levels?
Increased HHb can result from poor oxygen delivery, lung disease, circulatory problems, or being at high altitudes.
Is Deoxyhemoglobin dangerous?
Not by itself — it’s a normal part of oxygen transport. However excess HHb relative to O2Hb may signal a problem with oxygenation.
How is HHb measured?
Usually through blood gas analysis or pulse oximetry, which estimates the balance of oxygenated and deoxygenated haemoglobin.
Final Thoughts: Why HHb Matters
The HHb medical abbreviation might seem like a small detail, but it represents a vital part of how your body stays alive and well.
By understanding the balance between oxyhaemoglobin (O2Hb) and deoxyhemoglobin (HHb), healthcare professionals can:
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Detect oxygen problems early
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Manage patients in surgery or intensive care
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Monitor lung and heart function