Pharmacogenomic Testing for Statins: SLCO1B1

What pharmacogenomics means for statins

Pharmacogenomic testing for statins checks a few genes, mainly SLCO1B1, that change how much statin reaches your bloodstream and muscles. The result helps choose which statin and what dose, and expert guidelines say what to do with each result. Pharmacogenomics is the study of how your genes change the way a medicine works in your body. Two people can take the same pill at the same dose and end up with very different amounts of it in their blood. Some of that difference is inherited.

Statins show this well. They rank among the most studied medicines in the world, lower LDL cholesterol (LDL-C), and prevent heart attacks and strokes. People also stop them for muscle symptoms more often than any other drug. A handful of genes help explain why some people get much higher statin levels than others, and two expert groups have turned that evidence into prescribing advice:

• CPIC (the Clinical Pharmacogenetics Implementation Consortium), a US-based group, published its statin guideline in 2022. It covers SLCO1B1 for all statins, ABCG2 for rosuvastatin, and CYP2C9 for fluvastatin.
• DPWG (the Dutch Pharmacogenetics Working Group) published its SLCO1B1 and statins guideline in 2024.

Statin myopathy and other muscle symptoms

Statin muscle problems range from common aches to rare severe muscle breakdown, and genes matter most for the rarer, more serious end. Doctors group them under the name statin-associated musculoskeletal symptoms. The CPIC guideline describes three levels:

Statin myopathy, the middle level, is where the genetic evidence is strongest. Most cases seem to depend on how much statin reaches the muscle, which is why dose and drug interactions matter so much. CPIC notes that dose is the strongest single predictor, with roughly 6 times the risk on high doses compared with lower ones.

The aches at the top of the list behave differently. Blinded trials show that most of them show up on placebo too. Our guide to statin side effects: what's real covers that in detail. In short, a gene test can't tell you whether a particular ache came from your statin.

SLCO1B1: the gene that matters for every statin

The SLCO1B1 gene makes a transporter, also called OATP1B1, that sits on liver cells and pulls statins out of the blood and into the liver. The liver is where statins do their job. When the transporter works less well, more statin stays in the blood, and more of it reaches muscle.

The key variant is called c.521T>C (rs4149056). It appears in two versions of the gene, known as *5 and *15, and both are classified as no-function alleles. You have two copies of the gene, one from each parent, and the combination sets your predicted SLCO1B1 function:

• Increased or normal function: no variant that reduces function. Typical statin levels.
• Decreased function: one reduced copy, such as *1/*5 or *1/*15.
• Possible decreased function: one no-function copy plus one of uncertain function.
• Poor function: two reduced copies, such as *5/*5, *5/*15, or *15/*15.

The variant is common. In the DPWG review, the c.521C version shows up in about 14 to 22% of gene copies in people of European ancestry, 8 to 16% in East Asian populations, about 11% in Latin American populations, and less often in African (1 to 8%) and South Asian (about 5%) populations.

Why simvastatin gets the most attention

The link was found in a genome-wide study of people taking simvastatin 80 mg a day. Each copy of the C version raised the odds of myopathy about 4.5 times, and two copies raised it about 17 times. More than 60% of the myopathy cases in that study could be attributed to the variant.

Simvastatin is the statin most affected by SLCO1B1, which is why both guidelines are firmest about it. The effect on other statins is real but smaller, and for some of them the advice rests mainly on how much the gene changes drug levels in the blood rather than on proven side-effect differences.

What CPIC recommends for each statin

Here is a plain-language summary of CPIC's SLCO1B1 dosing table for adults. For people with normal or increased function, CPIC says to prescribe the usual starting dose of any statin.

CPIC keeps everyone with a reduced-function result on a statin by switching the statin, lowering the dose ceiling, or adding a second medicine such as ezetimibe. It rates its simvastatin advice as strong and most of its atorvastatin, pitavastatin, pravastatin, and fluvastatin advice as moderate, which reflects the thinner evidence for those drugs.

ABCG2: a second gene for rosuvastatin

ABCG2 makes a transporter (also called BCRP) that pushes certain drugs back out of cells, including in the gut and liver. A common variant, c.421C>A (rs2231142), lowers the amount of working transporter by about 30 to 40%. People with two copies had about 144% higher rosuvastatin levels in the blood than people with none.

CPIC's advice applies to rosuvastatin only:

• Normal or decreased ABCG2 function: usual starting dose.
• Poor ABCG2 function (two copies): start rosuvastatin at 20 mg or less. If more LDL lowering is needed, switch statins or add a non-statin medicine.

Because more rosuvastatin stays around, people with this variant also tend to get a bigger LDL drop from it. CPIC notes that the actual myopathy risk for this group is unknown, so the advice is to dose carefully, and rosuvastatin stays on the table.

This variant is about three times more common in East Asian populations than in European ones, and it helps explain why rosuvastatin levels run higher in people of Asian ancestry. For that reason, the FDA label starts people of Asian ancestry on 5 mg, a point we cover in rosuvastatin vs atorvastatin.

When someone has reduced function in both SLCO1B1 and ABCG2, CPIC offers optional advice to start rosuvastatin even lower, at 10 mg or less, since the effects are likely to add up. That recommendation is labeled optional because the combined data are limited.

CYP2C9: a gene for fluvastatin

CYP2C9 is a liver enzyme that breaks down fluvastatin (and many non-statin drugs, such as warfarin). Its two best-known reduced versions, *2 and *3, cut enzyme activity by about 30 to 40% and about 80%. CYP2C9 doesn't meaningfully affect the other statins.

• Intermediate metabolizers: start fluvastatin at 40 mg a day or less.
• Poor metabolizers: start fluvastatin at 20 mg a day or less.
• If more is needed, choose a different statin or add a non-statin medicine.

Fluvastatin is a lower-potency statin that is not prescribed often in the US, so this result rarely changes a plan. It can matter for other medicines, though, which is one reason a broad pharmacogenomic panel is sometimes more useful than a single-gene test.

What if you're already taking a statin?

Usually you can stay on it. If you've taken your statin without muscle problems for long enough, CPIC considers it reasonable to continue. Most gene results arrive after someone has been on a statin for years. CPIC gives practical advice for that situation:

• If your result puts your current statin and dose in a moderate risk category and you've taken it at least 4 weeks without muscle symptoms, it's reasonable to continue.
• If your result puts it in a high risk category and you've taken it at least a year without problems, CPIC considers it safe to continue.
• If you started more recently than that, your clinician may consider moving you to a lower-risk statin or dose.

CPIC is open that these time frames are based mostly on expert opinion and one simvastatin trial.

What the Dutch guideline says

DPWG looked only at SLCO1B1 c.521T>C and reached broadly similar, slightly more conservative conclusions:

• Simvastatin: choose a different statin for anyone who carries the variant. If there is truly no alternative for someone with one copy, keep the dose at 40 mg or less (for example by adding ezetimibe). With two copies, avoid simvastatin.
• Atorvastatin: only act if the person also has other significant risk factors for statin muscle problems. Then choose an alternative, or keep the dose as low as possible.
• Rosuvastatin: for carriers with other risk factors, keep the dose as low as possible, for example by adding ezetimibe.
• Pravastatin and fluvastatin: no change needed.

DPWG also rates how useful it is to test ahead of time: essential before simvastatin 80 mg a day, beneficial before lower simvastatin doses, and potentially beneficial before atorvastatin or rosuvastatin.

The two groups mostly agree and differ in format. CPIC gives statin-by-statin dose guidance for every gene result. DPWG reserves action for simvastatin and for people with other risk factors. Both agree on the big picture: avoid simvastatin with a reduced-function result, prefer a lower dose plus ezetimibe over a high dose of an affected statin, and keep people on lipid-lowering treatment.

Other things that raise statin muscle risk

Dose, drug interactions, age, and other health conditions often raise statin muscle risk more than genes do. CPIC lists these as well:

• Higher statin dose
• Drug interactions, for example cyclosporine, gemfibrozil, and some calcium channel blockers
• Older age and smaller body size
• Female sex
• An underactive thyroid and other metabolic conditions
• Intense physical exercise
• Asian or African ancestry
• Kidney or liver disease

A careful medication review often does as much as a gene test. Both together give the clearest picture.

Who might benefit from pharmacogenomic testing

Pharmacogenomic testing helps most when it could change which statin or dose you take. Testing is most likely to change a plan for people who:

• Are about to start simvastatin, especially at higher doses
• Have had muscle symptoms on two or more statins and want to know whether drug levels might be part of it, alongside a structured plan like the one on our statin intolerance page
• Need a high-intensity statin and have other risk factors for side effects
• Are of East Asian ancestry and are being considered for higher-dose rosuvastatin
• Take several medicines that interact with statins

People doing well on a statin, at goal, with no side effects, usually gain little from testing for statin reasons alone.

The limits of testing

• No trial yet proves gene-guided prescribing prevents muscle problems. CPIC notes that prospective data showing fewer side effects are lacking, though early studies show better attitudes toward statins and more appropriate prescribing.
• Most people with a variant do fine. A reduced-function result raises the odds, and most carriers still take statins without trouble.
• A test can miss rare variants. Many tests only check c.521T>C. Someone with a rarer reduced-function variant can be reported as normal by default. Which variants a lab checks matters.
• Results last a lifetime, including errors. A mistaken result could lead to an unnecessarily low dose. The safeguard is checking that your LDL actually falls as expected, with follow-up lipid testing.
• Some genes don't have enough evidence yet. CPIC reviewed CYP3A4, CYP3A5, and HMGCR and made no recommendations for them.
• Stopping statins altogether carries the bigger risk. Both guidelines warn against using a gene result as a reason to go without cholesterol treatment.

How Preval Health uses pharmacogenomics

Optional longevity genetic testing, which includes the SLCO1B1 statin gene, is offered at your first visit. Your clinician will tell you whether a test is likely to change your plan before you decide, and the test costs $499 one time. You can read more on our genetic testing page.

If you test, a licensed clinician in our partner telehealth network reviews the results with you and applies the CPIC guideline, within protocols written by a board-certified preventive cardiologist. Either way, treatment follows your LDL and ApoB numbers, with a target, labs to check progress, and non-statin options such as those in our alternatives to statins guide when a statin alone isn't the right fit. Preval runs as a cash practice.