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Astaxanthin Side Effects: Dose, and How Much Is Too Much
Astaxanthin has a reassuring safety record in the trials: a 2019 review of 87 human studies of natural astaxanthin, 35 of them at 12 mg a day or more, found none with a safety concern, and the European Food Safety Authority's 2020 assessment set an acceptable daily intake of 0.2 mg per kg of body weight, about 14 mg a day for a 70 kg adult, and judged 8 mg a day from supplements safe for adults on top of what food supplies.1, 2 The side effects people report are a harmless reddish skin tint at high intakes and mild stomach upset in a few; an 8-week trial at 6 mg found no change in blood chemistry, and 14 pooled trials found no change in blood pressure or blood sugar.3, 4 No interaction with a medicine has been documented, no human pregnancy data exist, and children under 14 exceed the daily limit at adult doses. What astaxanthin is and what it does covers the skin, eye and exercise trials; this page covers the dose.
What are the side effects of astaxanthin?
Few, and mostly cosmetic. The colour is the one people notice: astaxanthin is a red pigment, and a harmless reddish skin tint has been reported at high intakes, the same carotenoid effect as eating a great many carrots. Mild stomach discomfort, wind or nausea are reported occasionally, usually when a capsule is taken without food. In the 8-week safety trial, 35 adults aged 35 to 69 took 6 mg a day or placebo with meals, and the only differences in a full blood-chemistry panel were three tiny shifts the authors called clinically meaningless.3 Trials have run at 20 mg a day for 4 weeks in 32 trained cyclists and at 18 mg a day for 12 weeks in adults with raised triglycerides.5, 6 Across 14 randomised trials there was no change in blood pressure, fasting glucose or HbA1c, which also answers the fear that it might send either too low.4 Forum reports of headaches or dizziness have no trial counterpart; raise them with a pharmacist if they persist.
How much astaxanthin is too much?
The reference point is EFSA's acceptable daily intake of 0.2 mg per kg of body weight a day, derived from a two-year rat study in which liver-cell changes appeared at 40 mg per kg, with a 200-fold safety factor applied.2 That gives 10 mg a day for a 50 kg adult, 14 mg at 70 kg and 18 mg at 90 kg, counting what food supplies as well as the capsule. The 2020 assessment concluded that 8 mg a day from supplements plus a normal diet is safe for adults, that 14- to 17-year-olds reach the limit, and that children aged 10 to 14 exceed it by 28% at the same dose.2 In Great Britain the novel-food authorisation for the algal oleoresin caps supplements at 8 mg of astaxanthin a day, so any UK product sold inside the rules sits under the adult limit.7 "Too much", then, is a body-weight question: 12 mg is inside the limit for anyone over 60 kg, 24 mg exceeds it for anyone under 120 kg, and 36 mg exceeds it for anyone under 180 kg.
| Body weight | EFSA daily limit (0.2 mg/kg) | 8 mg a day | 12 mg a day | 24 mg a day |
|---|---|---|---|---|
| 50 kg | 10 mg | inside | over | over |
| 60 kg | 12 mg | inside | at the limit | over |
| 70 kg | 14 mg | inside | inside | over |
| 90 kg | 18 mg | inside | inside | over |
Can you take astaxanthin every day, and for how long?
Every day is how every trial used it, because a fat-soluble pigment builds up in membranes over weeks rather than acting on the day. The trials ran 4 to 16 weeks: 6 weeks for the eye-strain study, 8 to 12 weeks for most skin and lipid trials, and 16 weeks for the longest skin trial.6, 8, 9 Nothing has run for years, so "how long can you stay on it?" has no trial answer beyond four months; the acceptable daily intake is set as a lifetime figure, which is the regulator's way of saying that daily use inside the limit raised no concern in the toxicology. Decide what you are taking it for, judge it at 12 weeks, and review every three months. No trial has studied what happens on stopping.
Is astaxanthin safe for the kidneys and liver?
No human trial has reported a kidney or liver signal. The 8-week safety trial's panel included liver and kidney markers, all unchanged, and the one animal finding behind the daily limit was in rat liver cells at a dose 200 times the limit.1, 2, 3 Anyone with diagnosed kidney or liver disease asks their consultant before any supplement, not because of an astaxanthin signal but because that is the rule for every supplement in those conditions.
What should you not mix astaxanthin with?
No interaction with a medicine has been documented in people, which is different from proven absence, so the cautions below are theoretical. Blood-pressure and glucose-lowering medicines are the usual worry, because some people take it for blood pressure or blood sugar; the 14-trial pooling found it changed neither measure, so there is no evidence of an additive effect, and the sensible step is to tell your pharmacist what you take.4 Anticoagulants and antiplatelet medicines have a laboratory rationale (carotenoids and platelet function) and no human case or trial. Other carotenoids, beta-carotene and lutein among them, compete for the same absorption route in theory; no study has measured whether that matters at supplement doses. Vitamin D is the one real arithmetic: if your astaxanthin product also carries vitamin D, add it to any other vitamin D you take; can you take too much vitamin D has the upper limit. Vitamin C: no trial has tested the pair and there is no reason to expect a problem.
Who should avoid astaxanthin?
Children and adolescents, because EFSA's arithmetic puts under-14s over the daily limit at 8 mg and 14- to 17-year-olds at it; adult products are for adults.2 Pregnancy and breastfeeding: there is no human trial and no safety assessment in these groups, so it is a conversation with your GP or midwife, and the pack says so. People on several medicines, for the pharmacist reason above. Shellfish allergy is the common question and the answer is reassuring: supplement astaxanthin is extracted from the freshwater alga Haematococcus pluvialis, not from prawns or krill, so no shellfish protein is involved; the check is that the label names the alga, since a few products use krill oil instead.7 There is no astaxanthin-alone trial on testosterone or oestrogen, so anyone with a hormone-sensitive condition asks their team.
Morning or night, and with or without food?
With food, and no trial suggests time of day matters. Astaxanthin is fat-soluble, so it is absorbed with the fat in a meal; every trial gave it with meals, and taking it on an empty stomach is the most likely reason for a queasy capsule.3 No trial has compared morning with evening dosing and none has reported sleep as a side effect or measured it as an outcome, so "does astaxanthin affect sleep?" has no evidence either way; if a capsule seems to keep you up, move it to breakfast. This page is part of the metabolic series that begins with the Wellgard berberine guide.
Frequently asked questions
Is 36 mg of astaxanthin too much?
By EFSA's limit, yes for anyone under 180 kg: 36 mg a day is 0.2 mg per kg only at that weight.2 No trial on this page used it; the highest dose here was 20 mg for 4 weeks, and nothing above 12 mg has shown an extra benefit on skin.5, 8
Is it better to take 12 mg or 24 mg of astaxanthin?
No trial has compared 12 mg with 24 mg. The skin trials used 4 to 12 mg; in the 16-week trial, 6 mg and 12 mg both held wrinkle and moisture measures steady against placebo, and an inflammatory marker in the skin surface rose on placebo and 6 mg but not on 12 mg.8 24 mg exceeds the daily limit for anyone under 120 kg and is three times the GB supplement maximum, so in the UK the practical choice is 8 mg or under.2, 7
Can you take astaxanthin if you are allergic to shellfish?
Yes, if the label names Haematococcus pluvialis as the source, because the pigment is extracted from the alga and no shellfish protein is present. Avoid krill-oil products, which are shellfish.
Does astaxanthin affect sleep?
No trial has reported it as a side effect or measured sleep as an outcome. If you suspect it, take it with breakfast instead.
Is there any danger in taking astaxanthin?
At 8 mg a day, for an adult, the human record is 87 studies without a safety concern and a regulator's conclusion that the dose is safe; the open questions are years-long use, pregnancy and children, where there are no data rather than bad data.1, 2
Sources
- Brendler T, Williamson EM. Astaxanthin: how much is too much? A safety review. Phytotherapy Research, 2019. PubMed 31788888.
- EFSA Panel on Nutrition, Novel Foods and Food Allergens. Safety of astaxanthin for its use as a novel food in food supplements. EFSA Journal, 2020. PubMed 32874213.
- Spiller GA, Dewell A. Safety of an astaxanthin-rich Haematococcus pluvialis algal extract: a randomized clinical trial. Journal of Medicinal Food, 2003. PubMed 12804020.
- Xia W, et al. The effects of astaxanthin supplementation on obesity, blood pressure, CRP, glycemic biomarkers, and lipid profile: a meta-analysis of randomized controlled trials. Pharmacological Research, 2020. PubMed 32755613.
- Res PT, et al. Astaxanthin supplementation does not augment fat use or improve endurance performance. Medicine and Science in Sports and Exercise, 2013. PubMed 23274592.
- Yoshida H, et al. Administration of natural astaxanthin increases serum HDL-cholesterol and adiponectin in subjects with mild hyperlipidemia. Atherosclerosis, 2010. PubMed 19892350.
- Food Standards Agency. Novel food authorisations register for Great Britain. data.food.gov.uk.
- Tominaga K, et al. Protective effects of astaxanthin on skin deterioration. Journal of Clinical Biochemistry and Nutrition, 2017. PubMed 28751807.
- Sekikawa T, et al. Effects of diet containing astaxanthin on visual function in healthy individuals: a randomized, double-blind, placebo-controlled, parallel study. Journal of Clinical Biochemistry and Nutrition, 2023. PubMed 36777084.
General information, not medical advice: astaxanthin supplements are for adults; if you are pregnant, breastfeeding, have a diagnosed condition or take regular medicines, ask your GP or pharmacist before starting one.
