Blood sugar and diabetes

Advised

• Vitamin B12

  A vitamin found in foods of animal origin, such as milk, cheese, yoghurt and eggs, and added to some breakfast cereals.

  • MHRA: Low B12 is a common metformin side effect; levels are tested if symptoms suggest it.
  • NICE: Offered by mouth or injection while taking a medicine that causes the deficiency.

  Also covered by Diabetes UK, NHS and NICE.

  What vitamin B12 is, and the forms it comes in

• Folic acid before a pregnancy

  The man-made form of folate, a B vitamin found naturally in green leafy vegetables.

  • NICE: 5mg a day for women with diabetes planning a pregnancy, until 12 weeks of pregnancy.
  • Diabetes UK: Prescribed at 5mg: start at least 12 weeks before conceiving; not sold over the counter.

  Also covered by NHS and Diabetes UK.

  What folic acid before a pregnancy is, and the forms it comes in

Limited evidence

• Chromium

  A trace mineral found in meat, nuts and cereal grains.

  • NCCIH: Weak evidence on blood sugar; studies too varied to draw clear conclusions.

  Also covered by Diabetes UK and NHS.

• Cinnamon

  A spice made from the inner bark of cinnamon trees. Cassia, one common type, contains varying amounts of a substance called coumarin.

  • Mayo Clinic: Despite many studies, it is unclear whether it lowers blood sugar in diabetes.
  • Diabetes UK: Studied for blood sugar, but herbal remedies should never replace a treatment plan.

  Also covered by NCCIH.

• Berberine

  A compound found in plants such as barberry, goldenseal, goldthread, Oregon grape and tree turmeric.

  • NCCIH: A review's studies were mostly Chinese, some of poor quality, with widely varying results.
  • NCCIH: Not for use in pregnancy or breastfeeding, and may interact with some medicines.

• Apple cider vinegar

  Vinegar made by fermenting apple juice twice, about 5% to 6% acetic acid. Also sold as pills or gummies.

  • Cleveland Clinic: Most studies are small; more research is needed.
  • Cleveland Clinic: No standard dose; on blood sugar medicine, check with a doctor first.

• Magnesium

  A mineral found in spinach, nuts and wholemeal bread, among other foods.

  • NCCIH: Research so far is insufficient to base clinical guidelines on.
  • Diabetes UK: No evidence it can cause diabetes or stop it developing.

• Vitamin D

  A vitamin the body makes when skin is in sunlight. Oily fish, eggs and fortified foods have some; supplements come as D3 or D2.

  • Diabetes UK: No evidence it can cause diabetes or stop it developing.
  • NCCIH: Blood sugar changes in a 2022 review were small, below a clinically meaningful amount.

• Vitamin and mineral supplements

  Tablets of one or more vitamins and minerals, including multivitamins sold for people with diabetes.

  • Diabetes UK: Unless you have a deficiency or a prescription, no clear value for people with diabetes.

No good evidence

• Alpha-lipoic acid

  A compound found in many foods, including spinach, broccoli, potatoes, yams, carrots and red meat.

  • NCCIH: No better than placebo for blood sugar in a 2019 review of 10 studies.
  • Mayo Clinic: Results on diabetic nerve pain are mixed; larger studies are needed.

Things to check

• Diabetes UK: Keep taking diabetes medication, and tell your healthcare team about any herbal or complementary remedy.
• Diabetes UK: Supplements may affect how diabetes medicines work and make complications such as kidney disease worse.
• NHS: Medicines for diabetes, such as metformin, may not mix well with herbal medicines; check with a pharmacist first.
• MHRA: On metformin, seek medical advice for new extreme tiredness, a sore red tongue, pins and needles, or pale or yellow skin.
• NCCIH: Cassia cinnamon contains coumarin; large amounts might worsen liver disease.
• Mayo Clinic: Alpha-lipoic acid is risky when low on thiamin (vitamin B1); do not use it if you often drink large amounts of alcohol.
• NHS: 400mg or less a day of magnesium from supplements is unlikely to cause harm; more can cause diarrhoea.
• NHS: 10mg or less a day of chromium from food and supplements is unlikely to cause any harm.
• NHS: Do not take more than 100 micrograms (4,000 IU) of vitamin D a day.

If you take medication, are pregnant, or have a health condition, check with a pharmacist or GP first.