Statins: how they work, side effects and the blood values that shift

A statin lowers your LDL cholesterol by inhibiting an enzyme in your liver. Across an analysis of 170,000 participants, every 1.0 mmol/l drop in LDL came with roughly 22 percent fewer major vascular events (PMID 21067804). Most people know that part.

What they rarely hear is which blood values actually shift afterwards, and how fast.

I think that second half gets far too little attention. You take a tablet for months and nobody tells you what you should be seeing on paper. Below are the four values that respond, what the trials on side effects really show, and where the conversation with your GP starts.

What do statins actually do in your body?

Statins inhibit HMG-CoA reductase, the enzyme your liver uses to make cholesterol. Your liver compensates by pulling more LDL particles out of your blood. The result is a lower LDL value, usually visible after four to six weeks. Statins also appear to dampen inflammatory activity in the vessel wall a little.

Your liver makes most of your cholesterol itself. Food supplies a smaller share. That explains why a strict diet often lowers LDL less than people hope.

Inhibiting that enzyme triggers a second mechanism. Your liver cells place more LDL receptors on their surface, and those pull LDL out of your bloodstream. You see the effect in your LDL cholesterol and in your non-HDL value. If you want to understand those numbers first, read the difference between LDL and HDL.

Which statins exist, and how strong is mine?

In the Netherlands the common prescriptions are simvastatin, atorvastatin, rosuvastatin and pravastatin. They work through the same enzyme but differ sharply in strength per milligram. A low dose of a strong drug can do more than a high dose of a weak one. The STELLAR comparison mapped this in 2,431 people (PMID 12860216).

Two things stand out. Rosuvastatin 10 mg lowers LDL about as much as atorvastatin 40 mg. And pravastatin 40 mg lands near the level of simvastatin 10 to 20 mg.

So when your doctor switches you to a different drug, the milligram figure tells you very little. Someone moving from simvastatin 40 mg to rosuvastatin 5 mg sees a much smaller number on the box and still gets a comparable effect.

The second difference is solubility. Simvastatin and atorvastatin are lipophilic, meaning fat soluble, so they enter muscle and nerve tissue more easily. Pravastatin and rosuvastatin are hydrophilic and stay more within the liver. The Farmacotherapeutisch Kompas describes that difference drug by drug.

Which side effects occur, and how often?

The most reported complaints are muscle pain, muscle weakness and stomach or bowel trouble. How often they genuinely come from the pill is a separate question. In an analysis of 123,940 participants, 27.1 percent of statin users reported muscle pain, against 26.6 percent of people taking a placebo (PMID 36049498).

That gap is small. The researchers calculated that roughly 1 in 15 muscle reports among statin users could actually be attributed to the drug. In the first year it amounted to 11 extra reports per 1,000 person-years.

This does not mean the complaint is imagined. The pain is real. The cause is simply something other than the pill more often than people assume.

Rare but serious problems do exist. Severe muscle pain with loss of strength and dark brown urine warrants same-day contact with a doctor, because it can point to muscle tissue breakdown.

Why do some people get muscle pain from statins?

The exact mechanism is still unresolved. One frequently cited explanation is that statins also inhibit production of coenzyme Q10, which plays a role in the energy supply of muscle cells. Lipophilic statins enter muscle tissue more easily, which may explain part of the difference between drugs.

The SAMSON study reversed the question. Sixty people who had previously stopped because of side effects received, in random order, months of atorvastatin, months of placebo and empty months. Ninety percent of the symptom burden during statin months also appeared during placebo months (PMID 33196154). Half the participants restarted afterwards.

StatinWISE, with 200 participants in UK general practice, saw the same pattern: a mean difference of -0.11 on the symptom scale between statin and placebo months (PMID 33627334). What that means in practice is covered in our article on statin muscle pain and your CK value.

Which blood values shift on a statin?

Four values respond, each on its own timeline. Your LDL falls fastest. Your liver values may rise briefly and usually settle again. Your CK stays normal in most people. And your blood sugar drifts upward in some, measured over years rather than weeks.

Say you have two people who both start atorvastatin 20 mg. In one, LDL drops from 4.2 to 2.4 mmol/l and both ALT and CK stay comfortably inside the reference range. In the other, LDL drops from 4.2 to 3.6 mmol/l and ALT climbs from 28 to 51 U/l.

Same drug, same dose, two very different conversations at the GP. That is exactly why a baseline measurement beforehand is worth so much. Without that first reading, nobody knows whether an ALT of 51 is new or has looked like that for two years.

A lipid panel shows the cholesterol side. If you want the liver and sugar side alongside it, a metabolic panel gives a broader view of these markers.

Why is a statin often taken in the evening?

Your liver produces most cholesterol at night. Statins with a short half-life, such as simvastatin and pravastatin, therefore work better taken between dinner and bedtime. Atorvastatin and rosuvastatin stay active far longer, so timing barely matters with those two.

Simvastatin has a half-life of a few hours. Atorvastatin lasts around fourteen hours, rosuvastatin longer still. With those, what counts is taking the tablet every day, not when.

Grapefruit is a separate story. It inhibits the CYP3A4 enzyme that breaks down simvastatin and atorvastatin, so blood concentrations can climb. Pravastatin and rosuvastatin do not run through that route.

Which statins have the fewest side effects?

At group level the differences are narrower than people expect. What does show up in practice: people who developed muscle complaints on a lipophilic drug sometimes tolerate a hydrophilic one such as pravastatin or rosuvastatin better. A lower dose or an alternate-day schedule also happens.

Which route makes sense in your case is a conversation with your GP, not something to test on yourself. What you can do is write your complaints down precisely: which muscles, what time of day, and whether it coincided with starting or with a dose increase.

Those notes are worth a lot in the consulting room. They are the difference between "I have muscle pain" and "the pain sits in both thighs, started nine days after the increase to 40 mg, and is worse after stairs".

What happens when you stop a statin?

Your LDL returns to its pre-treatment level within a few weeks. The drug does not accumulate and has no lasting after-effect. There is no withdrawal, but the protective effect on your vessels disappears again, which is why stopping belongs in a conversation with your doctor.

If muscle complaints are the reason, a supervised temporary pause is often more informative than stopping for good. If the complaints fade within two to four weeks and return on restarting, that points toward the drug. If they persist throughout, the cause probably lay elsewhere.

That is precisely what makes SAMSON and StatinWISE so useful: they did this in a structured way, with a placebo in between, rather than on gut feeling.

Statins and your liver: how does that work?

A mild rise in ALT or AST occurs and usually resolves by itself. Serious liver damage from statins is rare. In the GREACE analysis, people with mildly abnormal liver values and heart disease received a statin, and their liver values actually improved while fewer cardiovascular events occurred (PMID 21109302).

Of the 880 statin users in that analysis, fewer than 1 percent stopped because of liver-related problems. That is a more reassuring picture than the package leaflet suggests.

So if you already have raised liver values, that is not an automatic reason to avoid a statin, though it is a reason to discuss it. More background in understanding liver values and in elevated liver values. A liver function test offers insight into these enzymes.

Statins, blood sugar and your weight

Statins appear to raise the chance of new-onset diabetes slightly. A meta-analysis of 13 trials with 91,140 participants found an odds ratio of 1.09 (PMID 20167359). Translated into practice: among 255 people taking a statin for four years, roughly one extra case of diabetes appears.

The researchers stressed that the reduction in heart attacks outweighs that effect for people at raised risk. Even so, it is a reason to let your HbA1c and your fasting glucose run alongside.

Weight is a separate debate, fed by a US analysis in which the BMI of statin users rose more over a decade than that of non-users (PMID 24763487). What sits behind that, and what it does not mean, is covered in atorvastatin and weight gain.

When your GP belongs in the picture

At every decision about starting, stopping, switching or changing the dose. Also with muscle pain that will not settle, with dark urine, with persistent nausea, or with yellowing of the skin or eyes. And with pregnancy or a wish to become pregnant, because statins are not used then.

What you can do is walk in with better information. A baseline of your LDL, ALT, CK and HbA1c before you start, plus a repeat a few months later, makes the conversation concrete. Some people choose to have that run periodically.

My advice stays simple: bring numbers, not impressions. A GP can do far more with a series of three measurements than with the sentence "I have felt different since I started taking this".

Frequently asked questions

How fast does a statin work?

The effect on your LDL is usually fully visible in a blood measurement after four to six weeks. You will not feel it yourself, because raised cholesterol causes no symptoms.

Can I drink alcohol on a statin?

Alcohol and statins both load your liver. Moderate use is not a problem for most people, but discuss it if your liver values are already raised. See also high cholesterol.

Do I need to fast before a cholesterol measurement?

For a standard lipid panel, fasting is often no longer required. Triglycerides do respond to a recent meal. Follow the instruction you receive with your appointment.

Does food still help if I already take a statin?

Yes, the effects partly stack. Plant sterols at doses of 0.6 to 3.3 grams a day lowered LDL by 6 to 12 percent on average in a meta-analysis of randomised studies (PMID 24780090). What else works is covered in lowering cholesterol without medication.

References

1. Cholesterol Treatment Trialists Collaboration. Efficacy and safety of more intensive lowering of LDL cholesterol. Lancet. 2010;376(9753):1670-1681. PMID 21067804.
2. Jones PH, Davidson MH, Stein EA, et al. Comparison of the efficacy and safety of rosuvastatin versus atorvastatin, simvastatin, and pravastatin across doses (STELLAR Trial). Am J Cardiol. 2003;92(2):152-160. PMID 12860216.
3. Cholesterol Treatment Trialists Collaboration. Effect of statin therapy on muscle symptoms. Lancet. 2022;400(10355):832-845. PMID 36049498.
4. Wood FA, Howard JP, Finegold JA, et al. N-of-1 Trial of a Statin, Placebo, or No Treatment to Assess Side Effects. N Engl J Med. 2020;383(22):2182-2184. PMID 33196154.
5. Herrett E, Williamson E, Brack K, et al. Statin treatment and muscle symptoms: series of randomised, placebo controlled n-of-1 trials. BMJ. 2021;372:n135. PMID 33627334.
6. Athyros VG, Tziomalos K, Gossios TD, et al. Safety and efficacy of long-term statin treatment in patients with abnormal liver tests (GREACE): a post-hoc analysis. Lancet. 2010;376(9756):1916-1922. PMID 21109302.
7. Sattar N, Preiss D, Murray HM, et al. Statins and risk of incident diabetes: a collaborative meta-analysis. Lancet. 2010;375(9716):735-742. PMID 20167359.
8. Sugiyama T, Tsugawa Y, Tseng CH, et al. Different time trends of caloric and fat intake between statin users and nonusers among US adults. JAMA Intern Med. 2014;174(7):1038-1045. PMID 24763487.
9. Ras RT, Geleijnse JM, Trautwein EA. LDL-cholesterol-lowering effect of plant sterols and stanols across different dose ranges. Br J Nutr. 2014;112(2):214-219. PMID 24780090.

Every blood test result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.