saudigastro.com/patients/folate-zinc-micronutrients
This article is educational and does not replace your doctor's advice. Seek urgent care for any red-flag symptoms.
Drug class
Dietary supplements (vitamins and minerals)
Examples
Folic acid (the supplement form of folate); zinc sulfate, gluconate or acetate; magnesium citrate, glycinate or oxide; selenium; vitamins A, E and K in water-miscible forms; multivitamin and mineral products. Brand names differ.
How it works
These micronutrients are needed in small amounts for blood cells, immunity, healing, nerves, muscles and the liver, and the gut or liver disease can lower them through poor absorption, loss in diarrhoea or stoma output, reduced intake, increased needs, or medicines. Folate (vitamin B9) is needed to make DNA and red blood cells; sulfasalazine (used in ulcerative colitis) reduces folate absorption and methotrexate blocks folate use, so folic acid is commonly prescribed with them, which also lowers methotrexate side effects such as mouth ulcers, nausea and abnormal liver tests. Zinc supports healing, taste and immunity; zinc is lost in chronic diarrhoea and from short bowel or high stoma output, and is often low in cirrhosis. Magnesium is lost in diarrhoea and short bowel and is lowered by long-term acid-reducing medicines (proton pump inhibitors, which carry a regulatory warning about low magnesium after prolonged use). Selenium may be low in short bowel, Crohn’s disease and long-term intravenous feeding. Vitamins A, E and K are absorbed with fat, so they run low when fat absorption fails: in cholestatic liver disease (PBC, PSC, biliary atresia), chronic pancreatitis and cystic fibrosis, coeliac disease, short bowel and after some weight-loss operations. Evidence is strongest for correcting proven deficiency. For general health, supplements do not clearly help people with normal levels, and for some (such as selenium and vitamin E) high intake in people who are not deficient has not shown benefit and may cause harm. The WHO recommends zinc as part of treatment for children with acute diarrhoea, where zinc deficiency is common, but this benefit is mainly shown in children in populations at risk of deficiency, and your child’s doctor should advise.
What it treats
- Folate: preventing folate deficiency and side effects with sulfasalazine and methotrexate; treating macrocytic anaemia from poor absorption (coeliac disease, small-bowel Crohn’s), alcohol or poor intake; preventing neural tube defects when planning pregnancy
- Zinc: low zinc in chronic diarrhoea, short bowel and stoma losses, cirrhosis and after bariatric surgery; acute diarrhoea in children in at-risk settings (WHO advice); Wilson disease is treated with zinc by a liver specialist, which is a different use
- Magnesium: low magnesium from diarrhoea, short bowel, long-term acid-reducing medicines, alcohol or diuretics, which causes cramps, tremor and heart rhythm problems
- Vitamins A, E and K: deficiency in fat malabsorption, cholestatic liver disease, pancreatic insufficiency and after some weight-loss surgeries
- Selenium: confirmed deficiency, mainly in short bowel and long-term intravenous feeding
How to take it
Do not start several supplements on your own. Ask for a blood test first, because you might not be deficient and too much of some nutrients is harmful. Your doctor or dietitian chooses which nutrient, which form, how much and for how long; the right amount differs for each person and condition. Folic acid with methotrexate is usually taken on a different day from the weekly methotrexate dose, as your doctor tells you. Check vitamin B12 before or along with folic acid, because folic acid can partly correct the anaemia of B12 deficiency while nerve damage continues. Fat-soluble vitamins (A, E, K) are best taken with a meal containing fat or with pancreatic enzymes if prescribed, and water-miscible forms are used when fat absorption is poor. Zinc is better tolerated with food but absorbed better on an empty stomach, and it competes with copper and iron. Magnesium taken by mouth often causes loose stools; slow-release or divided forms are better tolerated. Choose registered products, and keep to the label. Safe upper intake levels for adults from all sources (food plus supplements), set by the Institute of Medicine, are about 1,000 micrograms a day of folic acid from supplements and fortified foods, 40 mg a day of zinc, 400 micrograms a day of selenium, and 3,000 micrograms a day of preformed vitamin A; for supplemental magnesium it is 350 mg a day. These are ceilings for the general population, not targets, and a specialist may treat above them under monitoring.
Common side effects
- Nausea, stomach upset, metallic taste or loose stools with zinc and magnesium
- Mild nausea, bloating or poor appetite with folic acid at higher amounts
- Loose stools and abdominal cramps with oral magnesium
- Fishy or garlic breath with selenium, and bruising or an unusual taste with some fat-soluble vitamin products
Serious side effects — call your doctor
Numbness, tingling, balance problems, weakness, anaemia or frequent infections while taking zinc for a long time
Too much zinc can cause copper deficiency affecting blood and nerves. See your doctor for blood tests and stop high-dose zinc until advised.
Persistent vomiting, severe belly pain, headache, blurred vision, bone pain or yellow eyes or skin while taking vitamin A
Too much vitamin A can harm the liver, raise pressure in the head and weaken bones. Stop it and seek urgent medical advice. High-dose vitamin A must be avoided in pregnancy.
Hair or nail loss, garlic breath, skin rash, or nerve symptoms with selenium
May be selenium toxicity (selenosis). Stop and see your doctor.
Muscle cramps, tremor, palpitations or fainting (low magnesium or potassium), or marked weakness, slow heartbeat or breathing trouble after taking magnesium with kidney disease
Abnormal magnesium levels can affect the heart. Go to the emergency department. People with kidney disease should not take magnesium supplements without medical advice.
Easy bruising, nosebleeds, bleeding gums, black stools or blood in vomit or urine (possible vitamin K deficiency or bleeding)
Needs urgent blood tests; go to the emergency department if bleeding is heavy or you vomit blood. If you take warfarin, keep your vitamin K intake steady and do not start vitamin K without telling your doctor.
Night blindness or dry eyes (low vitamin A), unsteady walking, loss of sensation or weak muscles (low vitamin E), or new anaemia, sore tongue and mouth ulcers (low folate)
Possible deficiency despite treatment or lack of treatment. See your doctor promptly; do not wait for it to get worse.
Interactions
Zinc and magnesium reduce absorption of quinolone and tetracycline antibiotics, levothyroxine, bisphosphonates and iron, so take them at different times; ask your pharmacist how far apart. Zinc competes with copper, and iron competes with zinc. Folic acid can lower the effect of some anti-seizure medicines and interacts with methotrexate and trimethoprim in complex ways; take it exactly as your doctor advises. Acid-reducing medicines, diuretics and some chemotherapy can lower magnesium. Warfarin is affected by vitamin K intake, and by high-dose vitamin E; orlistat and bile-acid binders reduce absorption of vitamins A, D, E and K. Alcohol lowers folate, zinc and magnesium and increases liver risks from vitamin A. Always show your doctor and pharmacist everything you take, including herbal products and multivitamins. For iron and B12, see our separate page.
Monitoring
Tests depend on the condition: folate (serum or red-cell) together with B12 and a blood count; zinc (interpreted with inflammation and albumin, since levels can be falsely low during illness); magnesium (with potassium and calcium); selenium; vitamin A (retinol), vitamin E (with blood fats), and vitamin K status through clotting tests (INR) or specific tests. For methotrexate and sulfasalazine, blood counts and liver tests are monitored regularly. People with long-term malabsorption, short bowel, or cholestatic liver disease are usually checked at least once a year, and after any change in treatment. Interpreting low results needs your doctor, as inflammation can lower some levels without true deficiency.
When and how to stop
Do not stop or restart on your own. Some supplements are short courses to correct a deficiency, while others (such as folic acid with methotrexate, or vitamins in fat malabsorption) continue as long as the cause continues. Stop and call your doctor if you develop signs of excess, or if you become pregnant while on any high-dose or unusual supplement (especially vitamin A or methotrexate).
Pregnancy & breastfeeding
Folic acid is advised before conception and in early pregnancy to prevent neural tube defects; women with bowel disease, coeliac disease, on sulfasalazine or with obesity may need higher amounts, which your doctor decides. Methotrexate must be stopped well before trying for a baby (follow your specialist’s advice on timing) because it can harm the baby. Avoid high doses of vitamin A (preformed retinol) in pregnancy because they can cause birth defects, and avoid taking zinc, selenium or magnesium in high doses without advice. Wheat flour in Saudi Arabia is fortified with folic acid and iron under national policy, but this is not enough for planned pregnancy in everyone.
In the Saudi context
Good food sources include liver in small amounts (but limit it in pregnancy because of vitamin A), leafy greens such as spinach and jarjir (rocket), legumes (lentils, chickpeas, fava beans), fortified bread and cereals for folate; meat, chicken, seeds, legumes, dairy and seafood for zinc; nuts, whole grains, legumes and leafy vegetables for magnesium; and eggs, fish, olive oil, nuts and green vegetables for vitamins E and K. In Ramadan, medicines taken with food (folic acid, zinc, fat-soluble vitamins) can be moved to iftar or suhoor on your doctor’s advice; weekly methotrexate day and fasting need a plan. Beware of “immune booster”, “detox” or herbal products sold online or in shops; some contain very high doses of zinc, selenium or vitamin A, or hidden drugs. Choose products registered by the SFDA and tell your doctor about all you take.
Questions to ask your doctor
Save this list or print it before your appointment — doctors appreciate prepared patients.
- Which of these nutrients should be tested in my condition, and how often?
- Do I need folic acid with my methotrexate or sulfasalazine, and on which days?
- Is my zinc, magnesium or vitamin A level really low, or could inflammation explain the result?
- How long should I take each supplement, and when will it be rechecked?
- Can my multivitamin or herbal product cause harm with my medicines or pregnancy plans?
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Status: Approved for publication by SGA; individual clinician review is ongoing · Published 24/04/2026
For general education only; it does not replace your doctor’s advice. Individual clinician review of this guide is ongoing. SGA clinician? Review this guide