L-Carnitine Dosing and Safety

safety

Allergies

Avoid in individuals with a known allergy or sensitivity to carnitine.

Side Effects and Warnings

In general, L-carnitine is safe, and no significant complications have been reported in available human clinical studies. However, individuals must be sure to use only L-carnitine preparations with ≥99% enantiomeric purity.
Minor adverse effects reported by people have included abdominal cramping, abdominal discomfort, aggression, anxiety, back pain, bilateral ptosis (drooping eyelids), body odor, colitis symptoms, constipation, depression, diarrhea, euphoria, facial paresthesia (abnormal sensations), fatigue, fatigue in chewing, "fishy smell," gastralgia (stomach pain), gastric pyrosis (heartburn), gastrointestinal (stomach and intestinal) symptoms, headache, insomnia, loose bowel movements, low birthweights, mania, nausea, nervousness, psychosis, skin rashes, temporary hair loss, vomiting, and weakness. Serious adverse effects reported by people have included bronchitis, chronic obstructive pulmonary disease (long-term lung disease), and pulmonary embolism (blot clots in the lungs).
According to animal studies, carnitine may also cause endometriosis (growth of endometrial tissue outside the uterus), infertility, reduced heart contracture after a heart attack, and a slower heart rate increase after a heart attack,
When applied to the skin, carnitine may cause a burning sensation, increased dandruff, itching, and reddish bumps.
Carnitine may cause high blood pressure, although animal studies have also indicated that carnitine may cause low blood pressure. Caution is advised in people taking drugs, herbs, or supplements to lower blood pressure, as carnitine may affect these agents.
Carnitine may lower blood sugar levels. Caution is advised in people with diabetes or hypoglycemia, and in those taking drugs, herbs, or supplements that affect blood sugar. Blood glucose levels may need to be monitored by a qualified healthcare professional, including a pharmacist, and medication adjustments may be necessary.
Use cautiously in patients with alcohol-induced liver cirrhosis (liver disease), gastroesophageal reflux disease (GERD), insomnia, irritable bowel syndrome (IBS), long-term hepatitis C, mental illness or a risk of mental illness, narcolepsy, peripheral vascular disease (blocked arteries in the legs), preexisting gastrointestinal (stomach and intestinal) conditions, respiratory (breathing) disorders, or sleeping disorders, as well as in women and those on hemodialysis.
Use cautiously in patients taking anticoagulants, beta-blockers, or calcium channel blockers.
Use cautiously in low-birthweight infants due to potential for decreased weight gain. Individuals should make sure that L-carnitine prescribed to neonates (newborns) is justified and appropriate.
Avoid using in women who are pregnant or lactating, as well as in children.
Avoid using with D- or DL-carnitine.

Pregnancy and Breastfeeding

In pregnant women, carnitine may cause reduced levels of certain enzymes, free fatty acids, certain proteins, and triglycerides. Also carnitine may cause increased levels of carnitine and carnitine derivatives in the umbilical cord. Carnitine levels may be lower for pregnant women with gestational diabetes. Pregnant women with 3-methylcrotonyl-CoA carboxylase deficiency (3-MCC) deficiency may give birth to infants with increased levels of a certain form of carnitine.
In infertile men, carnitine may cause increased sperm motility and levels of seminal carnitine.
In preterm infants with respiratory distress syndrome, serum carnitine levels may be decreased. In newborns with isovaleric academia, carnitine levels may be increased.
In human infants, plasma free carnitine levels may be lowest for breastfed infants vs. formula-fed or mixed-fed groups.
In children with nonsyndromic cleft lip with or without cleft palate, malonyl-carnitine and acetyl-carnitine may be decreased.
Although the topic has not been well studied in humans, carnitine may cause the development of parthenogenetic embryos, endometriosis (growth of endometrial tissue outside the uterus), increased chorion weight and DNA/protein content, increased oocyte development and maturation, and infertility. Also, carnitine may influence growth catch-up rate after intrauterine growth restriction. L-carnitine consumption during pregnancy may improve the suckling behavior and weight gain of offspring.
Although the topic has not been well studied in humans, the level of carnitine in lactated milk may be affected by the presence of a protein called the OCTN transporter. Also, lactation may reduce levels of certain receptor proteins in the liver, which reduces carnitine production.
Although the topic has not been well studied in humans, L-carnitine may reduce the negative effects of oxidative stress on ovaries, oocytes, and embryos.
Although the topic has not been well studied in humans, L-carnitine may reduce the development of metabolic disorders during lactation.
Although the topic has not been well studied in humans, increased carnitine consumption by a pregnant individual may increase carnitine levels in the newborn, the offspring's birthweight, and growth during suckling. Increased consumption of carnitine and other herbs may improve the formation of the lining of the small intestines in neonates (newborns), although the effect of carnitine alone is unclear.
According to cell culture studies, carnitine uptake in human cells that provide nutrients to embryos may be reduced by lack of oxygen. Also, carnitine may increase the viability of maturing oocytes and affect the activity of certain enzymes, particularly those involved in antioxidant activity in premature neonates.
L-carnitine has been suggested as being an important nutrient during pregnancy.

dosing

Adults (18 years and older)

The U.S. Food and Drug Administration (FDA) recommends one gram of L-carnitine three times daily, intravenously (injected), for primary and secondary carnitine deficiency. This dose should not exceed three grams daily. Approximately 0.25-12 grams of carnitine (L-carnitine, acetyl-L-carnitine, and propionyl-L-carnitine) or 10-100 milligrams of carnitine per kilogram of body weight has been given by mouth 1-3 times daily, with 1-3 grams daily being the most common dose. Treatments have lasted for one week to 54 months. Single doses up to 15 grams have been given by mouth.
Carnitine has been taken by mouth to treat conditions including abstinence from alcohol (for alcoholics), aging, AIDS, Alzheimer's disease, amenorrhea (lack of menstrual period), angina (chest pain), antiretroviral toxic neuropathy (nerve damage), autism, cachexia (disease-induced weight loss), cardioprotection (protection of the heart) from chemotherapy agents, cardiovascular disease (heart disease) risk, chronic fatigue, congestive heart failure, depression, diabetes, diabetic neuropathy (nerve damage), dialysis (CAPD), Down syndrome, exercise performance, fatigue and depression associated with cancer, fatigue (celiac), fatigue (general), fatty liver disease, fibromyalgia, fragile-X syndrome, hepatic encephalopathy (confused thinking due to liver disorders), HIV, hyperlipidemia (high cholesterol), hyperthyroidism (overactive thyroid), infertility (male), insulin sensitivity, liver disease, medium-chain acyl-CoA dehydrogenase deficiency (MCAD), memory (in alcoholics), methadone withdrawal, multiple sclerosis, myocardial infarction (heart attack), obesity, peripheral neuropathy (nerve damage), peripheral neuropathy caused by chemotherapy, peripheral vascular disease, Peyronie's disease, pregnancy (miscarriage), primary and secondary carnitine deficiency, respiratory distress, Rett syndrome, sciatica, sickle cell disease, thalassemia, and varicocele (a widening of the veins along the cord that holds up a man's testicles), as well as for surgical uses (bypass).
For hair growth, a 2% carnitine solution has been applied to the scalp twice daily for six months.
Intravenous injections have also been used, with doses ranging from 10 to 100 milligrams per kilogram of body weight or 0.3-9 grams daily. Injections have been given for a duration of three days up to one year. Intramuscular injections have also been used, with doses typically being one gram of carnitine daily for 14-24 days. Injections should only be given under the supervision of a qualified healthcare professional, including a pharmacist.
Carnitine has been injected into the veins or muscle to treat conditions including alcoholism (abstinence), angina (long-term chest pain from clogged heart arteries), cardiovascular disease (heart disease) risk, cerebral ischemia (a lack of adequate blood flow to the brain), congestive heart failure, diabetic neuropathy (nerve damage), dialysis (CAPD), exercise performance enhancement, fibromyalgia, hepatic encephalopathy (confused thinking due to liver disorders), myocardial infarction (heart attack), peripheral neuropathy (numbness and pain in hands and feet caused by nerve damage), peripheral vascular disease (blocked arteries in the legs), primary and secondary carnitine deficiency, surgical uses (bypass), and valproic acid toxicity.
Parenteral doses of carnitine are determined for individuals based on stages of the life cycle and affected organs. Doses of 2-5 milligrams of carnitine per kilogram of body weight are given daily by the route used for the administration of macronutrients. Some sources suggest that pharmacologic supplementation should be 50-100 milligrams per kilogram of body weight daily.

Children (under 18 years old)

For attention-deficit hyperactivity disorder (ADHD), 500-1,500 milligrams of acetyl-L-carnitine has been given for 16 weeks.
For dialysis, 20 milligrams of carnitine per kilogram of body weight has been given by mouth daily for three months. L-Carnitine (50 milligrams per kilogram of body weight) has been given by mouth daily for two months.
For enteral use (in infants), 50 micromoles of carnitine per kilogram of body weight has been given through a gastric or nasogastric tube daily for seven days.
For hyperlipidemia (high cholesterol), three grams of L-carnitine has been given for up to six weeks.
For premature infants, 20 milligrams of carnitine per kilogram of body weight has been given daily by dosing the parenteral solutions with 130 milligrams of L-carnitine (Carnitor®, Sigma Tau Pharmaceuticals, Gaithersburg, MD) per liter and administering the supplemented PN solution at an infusion rate of 150 milliliters per kilogram of body weight. Also, 20 milligrams of L-carnitine (Carnitor®, Sigma Tau Pharmaceuticals, Gaithersburg, MD) per kilogram of body weight has been added to Pregestimil®, Nutramigen®, or Enfamil Premature® (Mead Johnson Nutritionals, Evansville, IN) formulas or expressed human milk daily for up to eight weeks.
For primary and secondary carnitine deficiency, 100-200 milligrams of carnitine per kilogram of body weight has been given by mouth daily over two or three doses. The U.S. Food and Drug Administration (FDA) does not recommend exceeding three grams of carnitine daily for primary and secondary carnitine deficiency.
For respiratory distress, 30 milligrams of L-carnitine per kilogram of body weight has been given daily in TPN until 120 milliliters per kilogram of body weight daily of enteral feedings were tolerated. Then 30 milligrams of carnitine per kilogram of body weight has been given by mouth daily.
For Rett syndrome, 100 milligrams of carnitine per kilogram of body weight has been given three times daily.
For total parenteral nutrition (TPN) for infants, 50 micromoles of carnitine per kilogram of body weight has been given daily for two weeks. Also, 10 milligrams of carnitine (L-carn®, Ildong Pharmaceutical Co Ltd, Seoul, Korea) per kilogram of body weight has been given for nine days.

interactions

Interactions with Drugs

Carnitine may lower blood sugar levels. Caution is advised when using medications that may also lower blood sugar. People taking drugs for diabetes by mouth or insulin should be monitored closely by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary.
Carnitine may interfere with the way the body processes certain drugs using the liver's cytochrome P450 enzyme system. As a result, the levels of these drugs may be decreased in the blood, and reduce the intended effects. People taking any medications should check the package insert and speak with a qualified healthcare professional, including a pharmacist, about possible interactions.
Although the topic has not been well studied in humans, carnitine may affect blood pressure. Caution is advised in people taking medications that lower blood pressure.
Many drugs influence the levels of carnitine in the body. Adefovir dipivoxil, anticonvulsants (carbamazepine, phenobarbital, and phenytoin), cephalosporins, doxorubicin, erythropoietin, penicillin derivatives (pivalate-containing antibiotics), polypharmacy, and valproic acid have been associated with low levels of carnitine in the blood. Lymphoblastoid interferon-alpha treatment may increase carnitine levels in the blood. The anticancer agent doxorubicin may increase levels of carnitine in the blood, although carboplatin, cisplatin, ifosfamide, and oxaliplatin resulted in increased elimination of carnitine in the urine. Carnitine levels may also be affected by natalizumab.
Although the topic has not been well studied in humans, 2,3-dimercapto-1-propanesulfonic acid may reduce carnitine excretion in urine. Paracetamol (acetaminophen) may cause carnitine deficiency. Aristolochic acid, cefepime, gentamicin, mildronate, pivalic acid, tacrolimus, and tetradecylthioacetic acid (TTA) may reduce carnitine levels. 3,4-Methylenedioxymethamphetamine (MDMA; Ecstasy) and triheptanoin may increase carnitine levels. Carnitine levels may also be affected by clofibrate and propiconazole.
Carnitine may reduce the negative side effects of several medications. Acetyl-L-carnitine may reduce pain and other negative effects of anticancer agents, as well as nerve damage caused by anticancer (cisplatin, paclitaxel) and HIV drugs. Carnitine may reduce heart toxicity caused by bupivacaine; fatigue caused by cyclophosphamide, ifosfamide, and interferon-beta; and liver and muscular damage caused by isotretinoin. Carnitine may also reduce the negative side effects of interleukin-2 (IL-2) and zidovudine. Decreased levels of carnitine have been associated with increased nerve damage caused by nucleoside analogs. Although the topic has not been well studied in humans, carnitine may reduce various negative side effects caused by acetaminophen, Adriamycin, carboplatin, ceftriaxone, cisplatin, doxorubicin, gentamicin, indomethacin, irradiation therapy, kidney toxins, liver toxins, methamphetamine, oxaliplatin, paclitaxel, and tilmicosin.
When used in combination, carnitine may improve the effects of certain drugs. Carnitine may increase the effects of acetylcholinesterase (ACE) inhibitors, agents used to treat hepatitis C (alpha-interferons), azithromycin, digoxin, drugs that promote urination, erythropoietin, hydroxyurea, nipecotic acid, orlistat, phosphodiesterase type 5 inhibitors (for sexual dysfunction), propafenone, ribavirin, sildenafil, and simvastatin. Although the topic has not been well studied in humans, carnitine may improve the effects of drugs for stomach and intestinal discomfort, leupeptin, and painkillers.
Carnitine may interact with agents for angina (chest pain), anti-inflammatory agents, beta-blockers, betaine, calcium channel blockers, cholesterol-lowering agents, cinnoxicam, exercise performance agents, fertility agents, glycosides, hair-growth agents, heart rate-regulating agents, immunomodulating agents, insulin, phenazopyridine, and potassium chloride. Although the topic has not been well studied in humans, carnitine may interact with agents that affect hearing loss, agents that affect the heart and blood vessels, agents that affect the nerves, agents used to treat opioid overdoses, Alzheimer's agents, antidepressants, antiobesity agents, bone agents, fertility agents, memory agents, mitoxantrone, nortriptyline, ocular agents, radioactive iodine, tilisolol, and wound-healing agents.
Although the topic has not been well studied in humans or animals, carnitine may reduce the negative effects of amiodarone, Also, carnitine may improve the effects of cisplatin. Carnitine may interact with agents that cause blood vessel widening, epirubicin, fluoroquinolones, grepafloxacin, levamisole, levofloxacin, OCTN2 inhibitors, progesterone, respiratory (breathing) agents, and thyroid hormones.

Interactions with Herbs and Dietary Supplements

Carnitine may lower blood sugar levels. Caution is advised when using herbs or supplements that may also lower blood sugar. Blood glucose levels may require monitoring, and doses may need adjustment.
Carnitine may interfere with the way the body processes certain herbs or supplements using the liver's cytochrome P450 enzyme system. As a result, the levels of other herbs or supplements may become too low in the blood. It may also alter the effects that other herbs or supplements potentially may have on the P450 system.
Carnitine may affect blood pressure. Caution is advised in people taking herbs or supplements that lower blood pressure.
Many herbs and supplements may influence the levels of carnitine in the body. Antibacterial herbs and supplements may decrease carnitine levels. Biotin, choline, and vitamin C may affect carnitine levels. Iron deficiency anemia may be associated with low carnitine levels. Vitamin B12 deficiency may cause increased carnitine levels.
Although the topic has not been well studied in humans, vitamin E (alpha-tocopherol) may increase carnitine levels. Lysine may reduce carnitine levels. Medium-chain triglycerides, sesame lignans, and stevia may affect carnitine levels.
Carnitine may reduce the negative side effects of several herbs and supplements. Carnitine may reduce the negative effects of antiviral herbs and supplements. Although the topic has not been well studied in humans, carnitine may reduce various negative side effects caused by branched-chain amino acids, copper, nickel,
Carnitine may interact with betaine, cholesterol-lowering herbs and supplements, exercise performance herbs and supplements, herbs and supplements that increase urination, herbs and supplements that prevent blood clotting or inflammation, immunomodulating herbs and supplements, licorice, mangosteen, and Wuzi Yanzong liquids.
Carnitine may interact with alpha-lipoic acid; antidepression herbs and supplements; antiobesity herbs and supplements; antioxidant herbs and supplements; arginine; biotin; caffeine; calcium; coenzyme Q10; fertility-enhancing herbs and supplements; fish oil; genistein; glycerophosphocholine; herbs and supplements that affect Alzheimer's disease, bone density, hearing, memory, the heart or blood vessels, the stomach or intestines, or vision; herbs and supplements that cause kidney damage, liver toxicity, or nerve damage; milk thistle; N-acetyl-cysteine; nicotinamide; painkillers; phosphatidylserine; S-adenosyl methionine; selenium; soy; St. John's wort; taurine; and wound-healing herbs and supplements.
Alpha-ketoglutarate may increase carnitine levels. Carnitine may interact with anticancer herbs and supplements, butyrate, conjugated linoleic acid (CLA), herbs and supplements that affect breathing, herbs and supplements that affect hair growth, lotus leaf extract, progesterone, and thyroid-influencing herbs and supplements.