Homocysteine: what a raised level means

Homocysteine is one of the less familiar markers in the Complete panel. It gets attention online as a heart risk marker, and a raised result can cause worry. In practice, homocysteine is most useful as a signal that something upstream needs checking, most often your B vitamins or your kidneys.

What homocysteine is

Homocysteine is an amino acid your body makes as it processes methionine, which comes from protein in food. It is a short-lived stop on a chemical pathway. Normally it is quickly recycled or broken down, and three B vitamins do most of that work: folate, vitamin B12 and vitamin B6.

If any of those vitamins is in short supply, homocysteine backs up in the blood like traffic behind a closed lane. That is why it is such a sensitive marker of B vitamin status, and why the Complete panel measures it alongside active B12 and folate.

What counts as raised

LifePrint uses the lab's printed range for homocysteine. By convention, a level above 15 umol/L is called hyperhomocysteinaemia. Mildly raised levels are common, particularly in older adults. Very high levels are rare and usually point to an inherited condition that affects the pathway, which needs specialist care.

Common reasons for a raised level

• Low folate. The World Health Organization's 2015 folate threshold of 10 nmol/L was chosen partly because homocysteine starts to rise below it.
• Low vitamin B12, which is more common with age, with a plant-based diet, and with some medicines, including metformin and long-term acid-reducing tablets.
• Reduced kidney function, because the kidneys help clear homocysteine. Your eGFR is in the same panel.
• An underactive thyroid.
• Smoking, heavy alcohol use and very high coffee intake.
• Some medicines that interfere with folate, such as methotrexate and certain epilepsy medicines.
• Older age and male sex, both of which tend to push levels up a little.

Homocysteine and the heart

Large studies have found that people with higher homocysteine have more heart attacks and strokes. For a while it looked like a promising new target. Then several large trials gave people B vitamins to lower their homocysteine. Levels came down, but heart attacks did not. Some studies suggested a small benefit for stroke in certain groups, but the overall result was disappointing.

The current view is that homocysteine is more of a marker than a cause for most people. It tends to be high when other risks are high, such as kidney disease, smoking and poor diet. For your heart risk, the markers that guide decisions are LDL cholesterol, ApoB, Lp(a), blood pressure, blood sugar and smoking. Homocysteine adds context but does not replace them.

What about MTHFR?

MTHFR is a gene involved in folate processing. Common variants in this gene are very widespread and can nudge homocysteine up, mainly when folate intake is low. Genetic testing for MTHFR is not recommended as a routine test by major genetics bodies, because the result rarely changes what a doctor would do. A normal folate level and a normal homocysteine are more useful than knowing your MTHFR type.

Getting a reliable result

Homocysteine is best measured fasting, which fits with the Complete panel's fasting requirement. A large protein meal shortly before the draw can raise it a little. Levels can also creep up if a sample waits too long before the lab processes it, so a surprising result is worth repeating before drawing conclusions.

What to do with a raised result

Look at your active B12, folate, eGFR and thyroid results in the same report. They often explain the finding. Then discuss the result with a registered healthcare practitioner, who can confirm any deficiency and decide on treatment. Avoid starting high-dose vitamins on your own before the cause is known, because folic acid can mask a B12 deficiency while the nerve damage continues.

Your LifePrint report shows where your homocysteine sits and points out related results. It is health information, not a diagnosis.