What cholesterol levels suggest FH? 

In the UK, familial hypercholesterolaemia (FH) is suspected when an adult has a total cholesterol level above 7.5 mmol/L or an LDL (bad) cholesterol level above 4.9 mmol/L. For children under 16, the thresholds are slightly lower, at 6.7 mmol/L for total cholesterol and 4.0 mmol/L for LDL. These levels are the primary clinical triggers for a GP to investigate a genetic cause for high cholesterol, particularly if they are paired with a family history of early heart disease. 

What We’ll Discuss in This Article 

• The specific Simon Broome cholesterol thresholds for adults and children. 

• How the Dutch Lipid Clinic Network (DLCN) score weights your lipid levels. 

• Identifying the ‘extremely high’ levels that suggest Homozygous FH. 

• The role of pre-treatment versus on-treatment lipid readings. 

• Physical indicators that, when combined with high levels, confirm a diagnosis. 

• Why the NHS systematically searches for younger people with total cholesterol over 7.5 mmol/L. 

• Using the BMI Calculator to manage broader cardiovascular risk factors. 

Simon Broome Diagnostic Thresholds 

The Simon Broome criteria are the most widely used tool in the UK for identifying potential FH. These criteria set clear ‘cut-off’ points for cholesterol levels. If your blood tests show results above these levels, you may be classified as having ‘possible’ or ‘definite’ FH depending on other factors like family history or physical signs. 

UK Simon Broome Cut-offs 

Patient Group	Total Cholesterol (mmol/L)	LDL Cholesterol (mmol/L)
Adults (16+ years)	Above 7.5	Above 4.9
Children (Under 16)	Above 6.7	Above 4.0

The Dutch Lipid Clinic Network (DLCN) Score 

The DLCN score is another validated tool used by UK specialists to calculate the probability of FH. Unlike the Simon Broome criteria, which use a fixed cut-off, the DLCN score gives more points for higher LDL levels. A total score of 8 or more is considered ‘definite FH’. 

LDL Levels and DLCN Points 

• LDL > 8.5 mmol/L: 8 points (suggestive of Definite FH on its own). 

• LDL 6.5 – 8.4 mmol/L: 5 points. 

• LDL 5.0 – 6.4 mmol/L: 3 points. 

• LDL 4.0 – 4.9 mmol/L: 1 point. 

If your LDL is significantly elevated (above 8.5 mmol/L), the DLCN score recognizes this as an almost certain indicator of a genetic mutation, even before DNA testing is conducted. 

Triggers for High-Priority Cases 

NHS clinical frameworks in 2026 have specific ‘red flag’ levels that trigger a systematic search of primary care records. These are the levels that suggest the highest risk of immediate cardiovascular complications. 

According to NICE (National Institute for Health and Care Excellence) guidelines, healthcare professionals are instructed to systematically search for: 

• People younger than 30 with a total cholesterol greater than 7.5 mmol/L. 

• People aged 30 or older with a total cholesterol greater than 9.0 mmol/L. 

Individuals in these brackets are considered at the highest risk of having FH and are prioritized for immediate specialist referral and cascade testing. 

Homozygous FH: The Most Extreme Levels 

While most people with FH have the ‘heterozygous’ form (inherited from one parent), a much rarer and more severe form exists called Homozygous FH (inherited from both parents). This form leads to extreme lipid elevations from birth. 

A clinical diagnosis of Homozygous FH should be considered in: 

• Adults with an LDL cholesterol greater than 13 mmol/L. 

• Children and young people with an LDL cholesterol greater than 11 mmol/L. 

Children with these levels often show physical signs like cutaneous xanthomata (fatty skin deposits) before the age of 5. These cases require urgent specialist referral to a tertiary lipid centre. 

Differentiation: Pre-treatment vs. On-treatment 

It is vital to use your pre-treatment lipid levels when checking against FH criteria. If you are already taking a statin, your current numbers will be artificially lower and may mask a genetic diagnosis. 

Feature	Diagnostic Significance
Pre-treatment Level	The ‘true’ level used for FH scoring and genetic referral.
Highest Ever Level	Can be used for diagnosis if pre-treatment records are lost.
On-treatment Level	Used to monitor the success of your medication (aiming for 50% reduction).

Clinicians will often look through your historical blood test records to find your highest recorded LDL or Total cholesterol concentration to ensure a genetic condition hasn’t been missed. 

To Summarise 

Cholesterol levels suggesting FH include a total cholesterol above 7.5 mmol/L or an LDL above 4.9 mmol/L in adults, and slightly lower thresholds in children. Extremely high readings, such as an LDL above 8.5 mmol/L, are highly suggestive of a definite genetic mutation. These thresholds are used within the Simon Broome and DLCN scoring systems to determine if a patient needs a specialist referral for DNA testing. Identifying these levels early is the key to preventing premature heart disease. 

If you experience sudden, severe chest pain, shortness of breath, or a sudden drooping of the face or weakness in the limbs, call 999 immediately. 

You may find our free BMI Calculator helpful for monitoring your overall health, as weight management is a crucial part of reducing the extra cardiovascular strain often found in patients with FH. 

Authority Snapshot 

Dr. Rebecca Fernandez is a UK-trained physician with an MBBS and experience in general surgery, cardiology, internal medicine, and emergency care. She has managed critically ill patients, stabilised acute trauma cases, and provided comprehensive care across inpatient and outpatient settings. This guide is based on 2026 clinical standards from the NHS and NICE regarding the identification and diagnosis of familial hypercholesterolaemia.