Health Guide


What is it?

Kelp is an herbal medicine taken from brown algae in salt water. It is used to treat weight loss, high blood pressure, low thyroid hormone, and arthritis. Kelp is also used to make the cervix (mouth of womb) open for childbirth or to end an early pregnancy. It is usually used as a source of iodine or salt.

Other names for Kelp include: Laminaria digitata, Laminaria japonica, Laminaria saccharina, Macrocystis pyrifera, Brown Algae, Horsetail, Sea Girdles, Seaweed, Sugar Wrack, Brown Seaweed, Algae, and Tangleweed.

Ask your doctor, nurse, or pharmacist if you need more information about this medicine or if any information in this leaflet concerns you.

Before Using:

Tell your doctor if you

  • are taking medicine or are allergic to any medicine (prescription or over-the-counter (OTC) or dietary supplement)
  • are pregnant or plan to become pregnant while using this medicine
  • are breastfeeding
  • have any other health problems, such as high blood pressure or heart or blood vessel disease


Talk with your caregiver about how much Kelp you should take. The amount depends on the strength of the medicine and the reason you are taking Kelp. If you are using this medicine without instructions from your caregiver, follow the directions on the medicine bottle. Do not take more medicine or take it more often than the directions tell you to.

To store this medicine:

Keep all medicine locked up and away from children. Store medicine away from heat and direct light. Do not store your medicine in the bathroom, near the kitchen sink, or in other damp places. Heat or moisture may cause the medicine to break down and not work the way it should work. Throw away medicine that is out of date or that you do not need. Never share your medicine with others.

Drug and Food Interactions:

Do not take Kelp without talking to your doctor first if you are taking:

  • Thyroid hormone medicine (examples: levothyroxine (Synthroid(R), Levothroid(R)), desiccated thyroid (Armor(R) thyroid)))


  • Before taking Kelp, tell your doctor if you are pregnant or breastfeeding
  • Arsenic poisoning has been reported with contaminated Kelp (2)
  • Kelp contains iodine. Taking too much can cause problems with your thyroid gland (3).
  • Acne may worsen if you take Kelp (6)

Side Effects:

Stop taking your medicine right away and talk to your doctor if you have any of the following side effects. Your medicine may be causing these symptoms which may mean you are allergic to it.

  • Breathing problems or tightness in your throat or chest
  • Chest pain
  • Skin hives, rash, or itchy or swollen skin

Other Side Effects:

You may have the following side effects, but this medicine may also cause other side effects. Tell your doctor if you have side effects that you think are caused by this medicine.

  • Kelp contains iodine. Taking too much can cause problems with your thyroid gland (3).
  • Problems with blood (such as low platelets or bleeding) and low blood pressure have been reported with the use of Kelp (1)
  • Acne (1)
  • Pain, fever, and cramping when used on the cervix (5)


1. Fetrow C & Avila J: Professional's Handbook of Complementary and Alternative Medicines. Springhouse Corporation, Springhouse, PA; 1999.

2. Walkin O & Douglas DE: Health food supplements prepared from kelp- a source of elevated urinary arsenic. Clin Toxicol 1975; 8:325-31.

3. Blumenthal, Busse, Goldberg, et al: The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. The American Botanical Council, Austin, TX; 1998.

4. Jurkovic N, Kolb N & Colic I: Nutritive value of marine algae Laminaria japonica and Undaria pinnatifida. Di Nahrung 1995; 1:63-66.

5. Lackritz R, Gibson M & Frigoletto F: Preinduction use of laminaria for the unripe cervix. Am J Obstet Gynecol 1979; 134(3): 349-350.

6. Krenek G & Rosen T: Cutaneous drug eruptions: patterns to help you identify the cause, control the problem. Consultant 1995; 35(9):1329-1337.

7. Ishizuki Y, Yamauchi K & Miura Y: Transient thyrotoxicosis induced by Japanese Kombu. Folia Endocrinol 1989; 65:91-98.

Last Updated: 7/4/2018
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