How Low is Low?

RISKS OF VERY LOW LDL CHOLESEROL LEVEL

By Laura Edith Chavez Salas
Universidad De Durango, Campus Zacatecas, Mexico

Amin H. Karim, MD
Houston Methodist Academic Institute

Low-density lipoprotein (LDL) represents a category of lipoprotein particles responsible for the transport of cholesterol and various lipids within the bloodstream. Often referred to as the “bad” cholesterol, it serves vital purposes. LDL particles serve as the primary carriers of cholesterol to peripheral tissues and consist of cholesteryl esters and triglycerides encased in a phospholipid shell, free cholesterol, and a single molecule of apolipoprotein B-100. Increased levels of LDL are directly associated with the onset of atherosclerotic cardiovascular disease (ASCVD), as LDL particles can penetrate the arterial wall, become retained and altered (for instance, oxidized), and facilitate the development of foam cells and atherosclerotic plaques. (1-4)

LDL exhibits heterogeneity, with subclasses that vary in size and density; smaller, denser LDL particles are deemed more atherogenic compared to their larger, more buoyant counterparts. (3, 5, 6) The cholesterol content within LDL particles is quantified as LDL cholesterol (LDL-C), which serves as a conventional marker for evaluating and managing cardiovascular risk. (7) Nevertheless, the quantity of LDL particles (LDL-P) and the concentration of apolipoprotein B (apoB) may offer further risk stratification, particularly in individuals with metabolic syndrome or diabetes, as discrepancies between LDL-C and LDL-P can arise. (8) Evaluation of ASCVD risk can be evaluated by assessing both LDL-C and LDL-P, asserting that the reduction of LDL—primarily through the use of statins and other lipid-lowering treatments—leads to a decrease in cardiovascular events. (4)

DANGERS OF VERY LOW LDL

However, an LDL-lowering regimen can lead to ultra-low-density lipoprotein cholesterol (LDL-C) levels. These are typically defined as <40–50 mg/dL, and especially <30 mg/dL. These levels are generally well tolerated and associated with a reduced risk of atherosclerotic cardiovascular disease (ASCVD), but several potential dangers have been identified. (9) Mechanistically, very low LDL-C may impair endothelial integrity and platelet function. This could potentially increase bleeding risk, especially for intracranial and gastrointestinal hemorrhage. (10, 11)

The most observed danger of ultra-low LDL is a possible hemorrhagic stroke and other bleeding events, particularly at LDL-C levels below 40 mg/dL, as supported by mechanistic and clinical data. Observational studies and meta-analyses have also reported a U-shaped relationship between LDL-C and all-cause mortality, with both very low (<50 mg/dL) and high (≥130 mg/dL) LDL-C levels associated with increased mortality in certain populations, such as those with coronary artery disease. (15)

There is also some evidence suggesting a potential association between ultra-low LDL-C and increased risk of new-onset diabetes mellitus, particularly with statin therapy. Leading to more complications, there is a possible link to cataract formation and glaucoma, though causality remains unproven and the absolute risk is low. (11, 14)

The main dangers of ultra-low LDL-C are a possible increased risk of hemorrhagic stroke, new-onset diabetes, and, less consistently, all-cause mortality in specific populations. However, for most high-risk patients, the cardiovascular benefits of aggressive LDL-C lowering outweigh these potential risks. (9-14)

HIGH-RISK PATIENTS

Patients at highest risk for complications associated with very low levels of low-density lipoprotein cholesterol (LDL-C) are:

• Individuals with a prior history of hemorrhagic stroke:

The American Stroke Association notes that the risk of hemorrhagic stroke with statin therapy is small and nonsignificant in those without prior cerebrovascular disease, but patients with a history of hemorrhagic stroke may be at increased risk, and lipid lowering in this group requires individualized consideration and further study. (16)

• Patients with poorly controlled hypertension and very low LDL-C:

There is literature that indicates that the combination of very low LDL-C (especially ≤40 mg/dL) and uncontrolled hypertension substantially increases the risk of both ischemic and hemorrhagic stroke. Although this risk is particularly more prevalent in East Asian populations, it is relevant globally. (17)

• Women with LDL-C <70 mg/dL:

There is evidence from long-term cohort studies in women that has shown that LDL-C <70 mg/dL is associated with a more than twofold increased risk of hemorrhagic stroke compared to LDL-C 100–129.9 mg/dL, independent of other risk factors. Meaning that women with no other risk factors have more risk than males with no other risk factors. (18)

• Patients on intensive statin therapy or with other risk factors for diabetes: Statin therapy, especially at high intensity, is associated with a modestly increased risk of new-onset diabetes. Particularly in those with predisposing factors such as metabolic syndrome or impaired fasting glucose. (11)

Risks associated with having ultra-low LDL-C are more prevalent in populations most at risk, which are those with prior hemorrhagic stroke, poorly controlled hypertension, women, and individuals with multiple vascular risk factors or on intensive lipid-lowering therapy. 

REFERENCES

  1. Orlova, E V et al. “Three-dimensional structure of low density lipoproteins by electron cryomicroscopy.” Proceedings of the National Academy of Sciences of the United States of America vol. 96,15 (1999): 8420-5. doi:10.1073/pnas.96.15.8420
  2. Rhainds, D, and L Brissette. “Low density lipoprotein uptake: holoparticle and cholesteryl ester selective uptake.” The international journal of biochemistry & cell biology vol. 31,9 (1999): 915-31. doi:10.1016/s1357-2725(99)00046-1
  3. Qiao, Ya-Nan et al. “Low-density lipoprotein particles in atherosclerosis.” Frontiers in physiology vol. 13 931931. 30 Aug. 2022, doi:10.3389/fphys.2022.931931
  4. Maurya, Rupesh et al. “Low density lipoprotein receptor endocytosis in cardiovascular disease and the factors affecting LDL levels.” Progress in molecular biology and translational science vol. 194 (2023): 333-345. doi:10.1016/bs.pmbts.2022.09.010
  5. Ivanova, Ekaterina A et al. “Small Dense Low-Density Lipoprotein as Biomarker for Atherosclerotic Diseases.” Oxidative medicine and cellular longevity vol. 2017 (2017): 1273042. doi:10.1155/2017/1273042
  6. Packard, C et al. “The role of small, dense low density lipoprotein (LDL): a new look.” International journal of cardiology vol. 74 Suppl 1 (2000): S17-22. doi:10.1016/s0167-5273(99)00107-2
  7. Jialal, I, and A T Remaley. “Measurement of low-density lipoprotein cholesterol in assessment and management of cardiovascular disease risk.” Clinical pharmacology and therapeutics vol. 96,1 (2014): 20-2. doi:10.1038/clpt.2014.69
  8. Galimberti, Federica et al. “Apolipoprotein B compared with low-density lipoprotein cholesterol in the atherosclerotic cardiovascular diseases risk assessment.” Pharmacological research vol. 195 (2023): 106873. doi:10.1016/j.phrs.2023.106873
  9. Karagiannis, Angelos D et al. “How low is safe? The frontier of very low (<30 mg/dL) LDL cholesterol.” European heart journal vol. 42,22 (2021): 2154-2169. doi:10.1093/eurheartj/ehaa1080
  10. Siniscalchi, Carmine et al. “Low LDL-Cholesterol and Hemorrhagic Risk: Mechanistic Insights and Clinical Perspectives.” International journal of molecular sciences vol. 26,12 5612. 11 Jun. 2025, doi:10.3390/ijms26125612
  11. Cure, Erkan, and Medine Cumhur Cure. “Emerging risks of lipid-lowering therapy and low LDL levels: implications for eye, brain, and new-onset diabetes.” Lipids in health and disease vol. 24,1 185. 21 May. 2025, doi:10.1186/s12944-025-02606-6
  12. Olsson, A G et al. “Can LDL cholesterol be too low? Possible risks of extremely low levels.” Journal of internal medicine vol. 281,6 (2017): 534-553. doi:10.1111/joim.12614
  13. Rong, Shuang et al. “Association of Low-Density Lipoprotein Cholesterol Levels with More than 20-Year Risk of Cardiovascular and All-Cause Mortality in the General Population.” Journal of the American Heart Association vol. 11,15 (2022): e023690. doi:10.1161/JAHA.121.023690
  14. Faselis, Charles et al. “Is very low LDL-C harmful?.” Current pharmaceutical design vol. 24,31 (2018): 3658-3664. doi:10.2174/1381612824666181008110643
  15. Scudeler, Thiago Luis et al. “Association between low-density lipoprotein cholesterol levels and all-cause mortality in patients with coronary artery disease: a real-world analysis using data from an international network.” Scientific reports vol. 14,1 29201. 25 Nov. 2024, doi:10.1038/s41598-024-80578-w
  16. Goldstein, Larry B., et al. “Aggressive LDL-C Lowering and the Brain: Impact on Risk for Dementia and Hemorrhagic Stroke: A Scientific Statement From the American Heart Association.” Arteriosclerosis Thrombosis and Vascular Biology, vol. 43, no. 10, Sept. 2023, https://doi.org/10.1161/atv.0000000000000164.
  17. Wu, Zhijun et al. “The risk of ischemic stroke and hemorrhagic stroke in Chinese adults with low-density lipoprotein cholesterol concentrations < 70 mg/dL.” BMC medicine vol. 19,1 142. 16 Jun. 2021, doi:10.1186/s12916-021-02014-4
  18. Rist, Pamela M et al. “Lipid levels and the risk of hemorrhagic stroke among women.” Neurology vol. 92,19 (2019): e2286-e2294. doi:10.1212/WNL.0000000000007454

To Treat or Not to Treat

A Panel Discussion Between Practicing and Experienced Cardiologists
on How to Tackle Risk Assessment in Asymptomatic People .

The case presentation and the comments that follow were interchanged on our WhatsApp groups APCNATeam in November 2024. This discussion presents an example of how experienced practicing cardiologist, faced with real life patients, navigate the findings on trials and papers and come to conclusion of what to tell the patient and how to proceed with the next preventive or therapeutic step. Please excuse any errors or omissions and will be happy to correct since the readers are themselves the Editorial Board. (Amin H. Karim MD)

Dr. Bashir Hanif
Need opinion on a 45 year old with positive family history of premature CAD. Asymptomatic. Very active, brisk walk n jog 45 minutes 6 days a week without symptoms.
CAC n Lipids are given below. What would you do next? Cath? Stress test? Or just Aspirin n high dose statins?

Abdul Hakeem
Where is the bulk of the calcium? If it’s a prognostically imp territory then I would get exercise MPS for further risk stratification. Agree with HD statin bring LDL<50 perhaps EPA
Salman Arain
I had the same question @Dr.Basheer Hanif – what is the distribution of calcium? 550 distributed over three vessels is less concerning than 350+ in the LM and proximal LAD. In the latter case, I may offer a stress test. Also, if the patient has a family history of premature CAD, then it may be reasonable to do a stress test.

Maryam Moten

Hussain Khwaja
I would do ASA and high dose statin to bring LDL between 25-50
Question is what we are going to do if stress test comes abnormal ?
Basheer Hanif
That was my problem too as this was the only report apparently they gave which doesn’t give distribution of calcium. He is completely asymptomatic despite heavy exertion.
Abdul Hakeem
So how does calcium scoring help in a very active asymptomatic person? Just creates a very pesky conundrum
Khurram Nasir
Preventive Management my friend, think beyond stenosis and intervention
Muhammad Saad
it can help to emphasize use of statins in asymptomatic patients
Khurram Nasir
Ldl below 55
Check Lpa if high family screening
ASA
SBP below 130
GLP1RA if diab pre diab
Further emphasize on diet and lifestyle
Abdul Hakeem
I have heard that and I’m sure there is some piece of evidence that it modifies human behavior but the consternation it causes seems to be its overwhelming impact!
Khurram Nasir
Few thoughts :
Make sure they’re not capturing any MAC

⁠ paradoxically the more number of vessels involved the more risk (prognostically) vs the more rationale thinking that if higher in one vessel possibly higher risk of stenosis or future risk

⁠ the relationship of high cac is not correlated with the stenosis in the same vessel, actually u may find often in the other with less score

⁠the issue is more distributive cac more turbulence in flow and more risk beyond plaque burden and rupture risk

⁠despite higher risk, majority don’t have event so no good way to assess who specifically is more at risk

⁠stress test not a bad idea in these uncertain cases
⁠hopefully pak Sehat with cac and CCTA in young Pakistanis will tell us what it means so kudos to bashir on leading the way

There is now huge body of evidence, actually, there is a meta-analysis from our group and JCC imaging that higher cac modifies, patient lifestyle, behavior, and attendance, and as well as physician behavior on prescription patterns

Also, as thought, from rationale thinking that it may increase anxiety and concerns, apart from few anecdotal cases, actually the evidence suggest otherwise

I see these patients all the time, it is how you message to them, that is great that you found out this,rather than waiting for an event to happen, and we have simpler an easier way to significantly modify the risk

Abdul Hakeem
Calcium score (in hugely asymptomatic)= demaagh me keera. The pt will find himself a Cardiol who will be more than happy to cath and stent him ( to prevent events
Khurram Nasir
I believe you; Well, just because there are bad practices, and some of these arguments have been made by long-term skeptics like David Brown even in the US, doesn’t mean that we stop doing the right thing

it means we start educating not only the patients, but also Cardiology community on what the best practices are

This is like saying we should stop screening for hypertension, because most of cardiologist will start on clonidine and may cause more harm

The same argument it’s gonna be made for anything
For deemagh me keera means more patient discussion and education and that means spending more time at the patient, unfortunately, that doesn’t exist much in most place even beyond Pakistan, and maybe that’s what we need to do, so we have more patient centric approach and care..
And btw asymptomatic doesn’t mean the person is not high risk for MI not only long term but also short term
Can’t think of any good rationale why the pt and pts physician wouldn’t want to know about so actually one can mitigate this totally preventable catastrophic complications and downstream issues like revascularization
Abdul Hakeem
I can’t agree more. I’m just saying unless we have solid evidence that “screening ca scores” in healthy asymptomatic individuals alters long term outcomes incrementally to usual practice we should be selectively doing calcium scores particularly in prevention rebellious pts
Khurram Nasir
First of all, this is old school, and things have changed: Let me help, explain,⁠ also, we need to put yourself in the patient’s shoes and ask ourselves whether we are better off in making a guess or knowing the actual risk and personalizing management accordinglyly

Cac test is no longer a screening test but more of a decision aid to guide risk and management, screening means that you do it for a person who is not candidate for a therapy, you find disease, intervene, and see if it improves. Here cac is also used for a lot of individuals who are already candidates for therapy, is to guide whether they need it or not and what intensity, so completely different philosophy.

⁠well proven to outperform any guesstimation approaches that you and Ion and others use in the clinic, and by the way, none of them have been tested in any randomized trial that using them improves outcome.. also by the way that I said I would be in a study that seeing a cardiologist improves outcome so maybe we can take everything with a grain of salt

⁠ as far as a pure screening approach and outcomes this concert there is a large study in Denmark, which is ongoing, and in the interim analysis has shhkwn 11% reduction in MI and stroke in the entire population, and three specified analysis, almost 11% all cosmetology reduction, and younger individuals
Abdul Hakeem
Thanks for the insightful comments khurram bhai. Always very scholarly and encyclopedic!
Syed Iqbal Rahmatullah
Repeat CAC to know the distribution or get the scan film to review.
High dose statin (goal LDL 30 to 40)
Aspirin
Lp a
Stress echo regardless of distribution
Life style adjustment. (Particularly dietary, HbA1c, BMI)

I had a similar patient yesterday, asymptomatic, played squash 5 days a week, and had very low LDL,
CAC 350, pakistani recently retired anesthesiologist, age 62, visiting his son here. No other risk factors.
SE showed anterior and inf wall hk, Rest echo 65%ef, post exercise 45%.
LHC showed discrete lesions but diffuse 3 vessel disease, extensive but good targets. Scheduled for cabg next week.
Farhan Katchi
I’ll just add that i use cac, as informed largely by Khurram’s body of work, and it has strengthened patient trust, buy in, compliance, and in my 7 years IMO better outcomes. My patients are more motivated to lose weight, eat better, exercise, and engage in escalating up medical preventative therapy when they know and understand the cac score concept (I show them the images in clinic on the screen so it’s concrete and not abstract). I have started to use LP(a) and ApoB in the same way that I use cac scores for risk adjudication, especially in women and the young where a cac of 0 may not tell the full longer term preventative story.
Bashir Hanif:


Syed Fazal:
Great discussion!
Now at the end of discussion, looks to like need one stent in type A lesion in mid cir, and all the above recommendations, for secondary treatment! Now he will need more anti platelets med for stent!
Bashir Hanif:
So who will put a stent and who would treat it medically. He is completely asymptomatic. It’s not a prognostic lesion!
Syed Arman Raza
Academic answer (in my view): no stent. Medical mgmt. Real world: stent + medical mgmt
Sabha Bhatti
Has he had functional testing ?If there’s ischemia in that territory you could consider stenting
Bashir Hanif:
You know functional study is going to be low risk and we are not going to change his prognosis/ risk of MI or mortality by putting a stent!!
Sabha Bhatti:
Yes but … Potentially that’s the bridge between academic and real world answer .. you have another justification for not stenting if there’s no ischemia
Bashir Hanif:
There will be ischemia. I can tell you what functional test is going to show. He jogs for 45 mins without symptoms. So it’s probably going to be medium size mild intensity ischemia at high work load. Will you send him to Hakim for stenting with this report?
Sabha Bhatti:
No one can do 45 min on a Bruce . Infact 16 min and few sec is the max I’ve seen . It helps to see symptoms , ECG and ofcourse vitals with exercise. No stent for now . Avoid oculostenotic reflex
Bashir Hanif:
I didn’t say 45 mins Bruce. I said jogs n brisk walk for 45 mins.
I advised him medical treatment. No stent
Ata Qureshi
This is a non prognostic, low risk lesion and I would manage it medically.
Syed Iqbal Rahmatullah
Bashir, was FFR done on left circ lesion? What was the rationale for doing cath, to begin with?
Bashir Hanif:
My point is it’s a non prognostic lesion pt is asymptomatic. Even if it had shown some ischemia or FFR was positive, in asymptomatic pt , would stenting change the risk of future MI or mortality??
I believe in CCS but if pt is symptomatic on GDMT or it’s a LM or may be Ostial LAD I would go for invasive approach and revasc. options. I don’t know about you and Hakeem but I had to relearn medical management of CCS when I moved back as lot of patients refuse to go for Revasc ( even LM n 3 VD ) and they are doing fine on medical management for years now. So as you said we need to resist oculostenotic reflex as much as possible!!( Disclaimer: I am an Interventionalist)
My 20 years of experience in Pakistan tells me Medical management can do wonders if done appropriately with belief!!
Abdul Hakeem
One our fellow intv cardiologist has classified this very well. Reasons for PCI in SIHD
if I can’t do it then GDMT
If I don’t do it someone else will
medical therapy until I return from vacation
Syed Fazal
I think most of us IC do lot more stents without evidence of mortality benefit.
Definitely there are regional differences for many other obvious reasons in different countries.
And as I said there is no consensus in this type A lesion.
Definitely in board exam don’t even think about stenting at this lesion!
Farhan Katchi
In cases of high cac, if I suspect LM or 3VD, I will Cath or CCTA to define anatomy for cabg referral. EXCEL and NOBLE and guidelines support revasc of this disease with cabg on account of its survival benefit even in asymptomatic patients. Now the ven diagram of asymptomatic and severe LM and significant 3VD is probably tiny especially if you consider 3V ischemic rather than anatomic disease and verify “asymptomatic” status on a treadmill
Haris Riaz:
I haven’t had a chance to follow this interesting discussion but ISCHEMIA trial frequently gets cited [sometimes even by people who haven’t actually read the full text or gone through the supplementary materials from nejm]. It might be interesting to note that:
One fifth patients in the conservative arm underwent revascularization
There are many other important limitations that need to be kept in mind before applicability. The trial [like COURAGE] reaffirms that medical management is effective in stable patients with stable symptoms compliant with GDMT.
Approximately one third of patients in ISCHEMIA had no angina in the last month before enrolment.
15% patients in ISCHEMIA had no objective evidence of ischemia on core lab assessment
One fifth patients in the invasive arm didn’t undergo revascularization