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Simvastatin side effects and how to avoid them

Simvastatin side effects include myopathy, constipation, and sleep problems

Common simvastatin side effects | Serious side effects | Cognitive side effects | Myopathy | Constipation | Side effects timeline | Contraindications | Warnings | Interactions | How to avoid side effects | How to treat side effects

Simvastatin—also prescribed as brand-name Zocor—is a generic prescription drug used to reduce total cholesterol, low-density lipoprotein cholesterol (LDL), and triglycerides (fats) in the bloodstream. 

Simvastatin treatment is most appropriate for people with high LDL cholesterol, high triglyceride levels, or hereditary high cholesterol. It’s also FDA approved to help prevent heart attack, stroke, and death in people with heart disease, blood vessel disease, or diabetes as well as people who have risk factors for cardiovascular disease. Statins are common prescription drugs. They block an enzyme—HMG-CoA reductase—responsible for the body’s synthesis of cholesterol. Healthcare professionals sometimes call them HMG-CoA reductase inhibitors, but it’s easier just to call them statins. Like other statins, simvastatin has a variety of possible side effects, including pain, liver problems, kidney problems, and raised blood sugar. In general, though, many people will find long-term treatment with simvastatin to be relatively problem-free.

Common side effects of simvastatin

Upper respiratory infections are the most common complaint among simvastatin users. In clinical trials, the incidence was close to 1 in 10 participants. In order of likelihood, side effects may include:

  • Upper respiratory infections
  • Headache
  • Stomach pain
  • Constipation
  • Atrial fibrillation
  • Nausea
  • Gastritis
  • Vertigo
  • Insomnia
  • Muscle pain
  • Fluid retention
  • Swollen sinuses
  • Liver problems
  • Memory problems and amnesia
  • Confusion

Serious side effects of simvastatin

The most serious side effects of simvastatin include:

  • Atrial fibrillation
  • Liver damage
  • Kidney failure
  • Muscle damage (rhabdomyolysis)
  • Tendon rupture
  • Blood disorders
  • Swollen pancreas
  • Diabetes
  • Lung disease
  • Lupus-like symptoms
  • Severe allergic reactions
  • Serious skin conditions

Can simvastatin cause sleep problems?

In simvastatin’s initial clinical trials, about 4% of participants reported problems with sleep. However, that was nearly the same incidence as participants who were given a placebo, indicating the drug may have little to do with the problem. A review of sleep studies concerning statins concluded that statins have no significant effect on falling asleep or staying asleep. Sleeplessness has many causes. If it’s a problem when taking simvastatin, ask the prescribing healthcare provider for medical advice. 

Cognitive side effects of simvastatin

Cognitive side effects, like memory problems and confusion, may be an issue with simvastatin and related drugs. The estimated incidence is that 1% of patients will experience memory impairment, 1% will experience amnesia (memory loss), and 1% will feel confused at times when taking simvastatin. These problems may be dose-related, meaning there is a greater risk at higher doses. Confusion and memory problems may significantly impair daily living. If this becomes a concern when taking simvastatin, report it to the prescribing healthcare provider. These problems usually improve when the drug is stopped.


Statins such as simvastatin are associated with muscle complaints, including damage, inflammation, and pain. People experiencing statin-induced myopathy report problems such as muscle pain, tenderness, cramping, weakness, and tendon problems. The exact incidence is unknown. Some estimate the incidence to be as high as 25%, but simvastatin’s clinical trials suggest the number may be closer to 4%. No one knows for certain why statins harm muscles in some people, but there may be higher risk due to age, genetics, medical conditions, and drug interactions. If simvastatin treatment is causing problems, talk to the prescribing healthcare provider. The dose may be reduced, or stopped if there is severe muscle damage.


Constipation is a common side effect of simvastatin. Initial clinical trials put the incidence at about 2%, but the real-world incidence may be more than 6%. If constipation occurs when taking any drug, the best advice is to consult with the prescribing healthcare provider. 

How soon do simvastatin side effects start?

Simvastatin’s peak concentration in the bloodstream occurs in about four hours. Some mild and serious side effects can occur early in treatment, while others take several weeks or months of treatment to become problematic. 

How long do simvastatin side effects last?

Some simvastatin side effects may improve over time. Others, including memory loss, cognitive impairment, and muscle pain, are reversible once the drug has been stopped. With a half-life of four to five hours, simvastatin levels fall to less than 10% of their peak in 10 hours. Typically, problems like headaches and nausea will resolve by then. Some problems, such as muscle damage, liver damage, or kidney damage may take longer to get better.

What are the long-term side effects of simvastatin?

Most healthcare professionals consider simvastatin a safe drug for long-term use. Many of the most publicized and severe side effects such as muscle problems, liver problems, kidney problems, and cognitive problems are typically delayed effects, so they are more likely to occur as simvastatin treatment persists or if doses go up.

Simvastatin contraindications

Because simvastatin’s side effects could worsen some conditions, simvastatin is never prescribed to people with:

  • Muscle disease
  • Liver failure or advanced cirrhosis
  • Allergy to statin drugs


Simvastatin should not be used during pregnancy, though the FDA does allow for its use in some individuals at high risk of complications from lipid disease. Simvastatin can harm the fetus, and statin treatment is usually not necessary during pregnancy.


Breastfeeding is not recommended for women who are taking simvastatin. Risks and benefits for individuals should be discussed with a healthcare provider.


Simvastatin is FDA approved to treat children 10 years of age and older for congenital high cholesterol (hypercholesterolemia). Because cholesterol is important for development, the use of statins in very young children is discouraged.


People older than 65 have an increased risk of muscle problems when taking simvastatin. In addition, simvastatin levels in the blood are higher in older people, so healthcare providers are urged to use doses that are as low as possible. Liver function as measured by blood tests will need to be regularly performed.

Simvastatin warnings

Although statins such as simvastatin are generally safe to take, some people may have problems requiring extra caution or monitoring.


Because of simvastatin’s side effects and its effects on the liver, it’s used with caution in people with:

  • Liver problems
  • Chronic alcohol abuse
  • Kidney disease
  • Diabetes
  • Underactive thyroid
  • People who may become pregnant

People of Chinese descent have an increased risk of developing muscle problems when taking simvastatin. Extra monitoring may be required. 

Abuse and dependence

Simvastatin is not a drug that has a high potential for abuse. There is no known risk for physical dependence. Although discontinuing simvastatin will not cause unpleasant withdrawal effects, anytime a statin is stopped, cholesterol levels may rise.


Call a poison control center or get medical attention if too much simvastatin is taken. Most people are prescribed 20–80 mg per day; the absolute maximum is 80 mg per day. Although there may not be immediate issues when exceeding the prescribed dose, repeated overdoses increase the risk of muscle or liver damage.

Simvastatin interactions

Because of potentially hazardous drug interactions, simvastatin is never prescribed with certain prescription drugs, including:

Most (but not all) of these drugs block the liver enzyme that breaks down simvastatin. The result is a hazardous increase in simvastatin serum levels, raising the risk of serious side effects such as muscle damage and liver damage. These contraindicated drugs are so good at blocking this enzyme that they can’t be safely taken with simvastatin. Other drugs also block this enzyme but not so powerfully. They can be used with simvastatin, but side effects must be monitored, and doses may need adjusting. These include:

Some drugs do the opposite: they speed up the body’s metabolism of simvastatin, reducing the ability of simvastatin to lower cholesterol and fats. These drugs include:

Finally, healthcare providers are wary about combining simvastatin, a drug that can damage muscles, with other drugs that can damage muscles. These include fibrate cholesterol drugs like fenofibrate, corticosteroids, some malaria drugs, and alcohol.

How to avoid simvastatin side effects

Though generally without problems, statin use can cause side effects. Sometimes side effects can be avoided. Here are a few tips to lower the risk.

1. Take simvastatin as directed

The best way to maximize the benefits and minimize side effects is to follow the instructions when taking this medicine. Above all, don’t take too much. If a dose is missed, it can be taken when remembered, unless it’s almost time for the next dose. In that case, skip the missed dose and take the next dose as scheduled to avoid taking too much at one time.

2. Take simvastatin in the evening

To maximize the benefits of taking this drug, take each dose in the evening. This may help with side effects, too.

3. Inform the prescriber about all medical problems

Besides taking the medicine correctly, another sure way to avoid the side effects of statins is to make sure the prescribing healthcare provider has a complete picture of your health conditions. For simvastatin, the prescriber will particularly need to know about:

  • Kidney disease
  • Liver disease
  • Diabetes
  • Hypothyroidism
  • Muscle pain or muscle weakness
  • Pregnancy or plans on getting pregnant
  • Breastfeeding or breastfeeding plans

4. Inform the prescriber about any drugs being taken

Drug interactions are another perennial source of side effects. Unfortunately, the list of drugs, supplements, and foods that cause problems with simvastatin is long. The best advice is to tell the prescriber about all over-the-counter and prescription drugs, supplements, and herbal remedies being taken.

5. Avoid alcohol

Drinking too much alcohol is not safe when taking simvastatin because it increases the risk that simvastatin will cause serious liver damage. Every once in a while is okay, but try to avoid overdoing it.

6. Avoid grapefruit

Believe it or not, grapefruit and grapefruit juice can increase the risk of simvastatin side effects. Healthcare professionals generally advise it be taken out of the diet. Cranberries and cranberry juice could also cause the same problem. So do niacin supplements, so talk to the prescriber if niacin or vitamin B3 supplements are part of the daily routine. 

7. Keep all follow-up appointments 

To avoid serious side effects, follow-up appointments are necessary. Regular blood tests, for instance, help detect problems with the muscles or liver before they blow up into serious medical conditions.

How to treat side effects of simvastatin

Most simvastatin side effects can be managed at home. Many will get better over time. Some side effects, though, will require the help of a healthcare professional.

Muscle problems

Stop taking simvastatin and contact a healthcare professional if muscles start to hurt or become weak. If simvastatin is affecting the muscles, it may become hard to lift your arms or climb stairs. A healthcare professional may need to perform a blood test to confirm that muscles are being damaged.

Memory problems

If things are easily forgotten, or you start feeling confused or disoriented, talk to the prescribing healthcare provider. Reduced doses may help, but some people may need to switch to a different statin or a different type of cholesterol drug.

Liver problems

If simvastatin starts affecting the liver, it may not be evident. Blood tests are usually required. Stop the drug and see a healthcare provider if any of these signs of liver problems are noticed:

  • Dark urine
  • Pale stools
  • Appetite loss
  • Throwing up
  • Tiredness
  • Yellowing of the skin or eyes