High homocysteine: what it means and what to do

A high homocysteine means your body is not clearing it well. Usually vitamin B12 or folate is short, sometimes the kidneys work less well. The cause can often be found and corrected. A very high result, or one that stays high, should be seen by a doctor.

What high homocysteine means

Homocysteine forms when your body uses protein. Clearing it needs B12, folate and B6. If one of them is short, homocysteine builds up in your blood.

How high it is matters. Just above 15, diet, coffee, smoking or a mild shortage are often behind it. Above 30 there is usually a marked shortage or a kidney problem.

A high homocysteine on its own is not a disease. It is a signal that tells you where to look.

What causes high homocysteine

There is often more than one. The most common come first.

• Too little vitamin B12: Common in people who eat few animal foods, with age, or with medicines such as metformin and stomach acid drugs.
• Too little folate: Common in people who eat few leafy greens and legumes, or drink a lot of alcohol.
• Kidneys working less well: Your kidneys help clear it. If they filter less, it rises.
• Smoking, lots of coffee, alcohol: All three go with higher levels.
• An underactive thyroid: Hypothyroidism can raise it. Treating the thyroid corrects it.
• The MTHFR gene variant: It is common and raises it a little, especially when folate is low.
• Some medicines: Methotrexate, anti-epileptics and levodopa, among others. Do not stop them on your own: talk to your doctor.

Symptoms of high homocysteine

High homocysteine on its own causes no symptoms. If there are any, they come from the cause, usually a shortage of B12 or folate. For example:

• Tiredness and shortness of breath, with anaemia
• Tingling or numbness in your hands and feet
• A red, smooth tongue, or frequent mouth ulcers
• Problems with memory or concentration

If you have these symptoms, talk to your doctor: a B12 shortage should be treated early.

High homocysteine and your heart

People with high homocysteine have, on average, more heart attacks, strokes and blood clots. For years the idea was that lowering it would protect the heart.

Trials say otherwise: with vitamins, homocysteine falls, but heart attacks do not. For stroke there may be a small benefit.

For your heart, cholesterol, blood pressure, smoking and blood sugar matter more. A high homocysteine is a good reason to check them.

Which tests to read alongside it

These tests help show where it comes from.

What your result means

The upper end of the scale, in µmol/L.

• 5 to 15: Normal. Your body clears it well. B12, folate and B6 are enough. Nothing to do. The lower it sits in this range, the better.
• 15 to 30: High. Often B12 or folate is low. Kidneys, thyroid, smoking, coffee and some medicines count too. Talk to your doctor: they usually check B12, folate and your kidneys.
• Above 30, up to 100: Very high. Usually a marked shortage of B12 or folate, or kidneys that work less well. See your doctor soon. The cause needs to be found and treated.
• Above 100: Extremely high. This is rare. It can be a severe B12 shortage or an inherited metabolic condition. See your doctor within a few days: they usually refer you to a specialist.

How to lower your homocysteine

It depends on the cause. Where to start:

• First, with your doctor, check B12, folate and your kidneys: the treatment depends on what is short.
• What to eat: leafy greens, legumes, citrus fruit and whole grains for folate. Fish, eggs and dairy for B12.
• If you eat few or no animal foods, B12 usually needs a supplement. Ask your doctor which one and how much.
• If you smoke, stopping helps. Drink less alcohol and less coffee.

Do not take high-dose supplements without asking your doctor: a B12 shortage needs to be found first, because folic acid alone can hide it.

High homocysteine: when to worry

Talk to your doctor if:

• Your homocysteine is above 15 µmol/L.
• It is above 30: see your doctor soon, the cause needs to be found.
• You have tingling, tiredness that does not go away or memory problems.
• You have had a blood clot, or heart attacks or strokes at a young age run in your family.
• It is above 100: see your doctor within a few days.
• You have sudden weakness in an arm or leg, a drooping mouth, trouble speaking or chest pain: call 112 or go to the emergency department.

Frequently asked questions

When is homocysteine a worry? Above 15 µmol/L it is worth talking to your doctor. Above 30 the cause should be looked for, soon. Above 100 is rare, and your doctor usually refers you to a specialist.

High homocysteine and low vitamin D: is there a link? They are often found together, but there is no direct link. They often share causes, such as a poor diet or little sun and movement. Each is looked at on its own.

Is high homocysteine inherited? Sometimes in part. A common variant of the MTHFR gene raises it a little, especially with low folate. Severe inherited forms are rare and give very high values, usually above 100.

How long does it take to come down? If a vitamin shortage is the cause, it usually falls within a few weeks of treatment. Your doctor has it checked again afterwards.

Do B vitamin supplements help? If there is a shortage, yes: they correct it and homocysteine falls. If there is none, taking them to protect your heart has not shown a benefit. Decide with your doctor.

Sources

• Refsum and colleagues, facts and recommendations about total homocysteine determinations: an expert opinion. Clinical Chemistry, 2004. PMID 14709635
• Homocysteine Studies Collaboration, homocysteine and risk of ischemic heart disease and stroke: a meta-analysis. JAMA, 2002. PMID 12387654
• Martí-Carvajal and colleagues, homocysteine-lowering interventions for preventing cardiovascular events. Cochrane Database of Systematic Reviews, 2017. PMID 28816346
• Hickey and colleagues, ACMG practice guideline: lack of evidence for MTHFR polymorphism testing. Genetics in Medicine, 2013. PMID 23288205